EP3247908B1 - Pumping unit with integrated separator, vacuum pump and liquid pump - Google Patents

Description

The present invention relates to a pump unit, in particular for a calibration tool of an extrusion system.

Extrusion systems for the production of extruded profiles, in particular extruded hollow profiles made of thermoplastic, usually have shaping devices with which the plastic profile strands emerging from an extrusion die of the extrusion tool, for example hollow profiles or pipes, are calibrated to the desired external and internal dimensions and in the desired dimensions frozen or cooled to the required temperatures to achieve the desired inherent rigidity. Vacuum calibration devices with integrated cooling devices are typically used for this purpose. The vacuum calibration device is designed such that the still plastic extruded profile is sucked onto the shaped surfaces of the calibration orifices of the calibration tool with the help of the vacuum applied. Cavities in the form of vacuum slots can be formed between the calibration orifices. For cooling the extruded and calibrated profiles, shaped surfaces can be used in which cooling channels for a temperature control medium, usually water, are left out. In addition, cooling devices such as water baths, spray baths and similar devices known to the person skilled in the art can be used. Extrusion systems with such calibration tools and corresponding cooling devices are for example in the Book by Walter Michaeli "Extrusion tools for plastic and rubber", Karl Hanser Verlag, Munich / Vienna, 2nd edition, 1991 , described. It also exemplifies the European patent application EP 0879132 A1 and referred to the prior art mentioned there.

Vacuum pumps are usually used to generate the negative pressure on the tool walls of the calibration tool. By cooling the extrudate with a liquid cooling medium, such as water, a calibration usually results in a fluid mixture comprising liquid and gaseous media, typically a water-air mixture, which has to be removed and separated.

In the German utility model DE 20206606 U1 describes a pump unit for a calibration tool of an extrusion system, which has a separator which has at least one fluid inlet for a fluid mixture, which comprises liquid and gaseous media, at least one fluid outlet and at least one gas outlet, means for generating a negative pressure in the separator which is associated with the gas outlet and communicate with the fluid inlet, means for aspirating the fluid, which communicate with the fluid outlet, and means for determining the level of the fluid in the separator. The separator is arranged between the calibration tool and a central vacuum pump. In the known device, the means for determining the level of the fluid in the separator comprise a float arrangement which interacts via an actuating device with a movable closure body arranged at the mouth opening of the fluid outlet, so that the fluid outlet is opened and closed as required depending on the height of the water level can be. This ensures that only liquid medium is always removed from the separator. In one embodiment, in the pump unit of the prior art, a cyclone separator is connected downstream of the first separator, which ensures that the liquid and gaseous medium are almost completely separated, so that suction of the liquid medium into the vacuum pump is avoided. In addition, the gas space of the cyclone separator can serve as a vacuum accumulator, so that a targeted build-up of vacuum in the individual vacuum tanks of the calibration tool is achieved with simultaneous separation of the media in the two separators. For this purpose, numerous throttle valves are arranged in the vacuum lines between the cyclone separator and the calibration tool.

This in DE 20206606 U1 Pump unit described, however, has disadvantages. The mechanical float and actuator in the first liquid separator is prone to failure. Furthermore, the setting of the vacuum in the calibration tool via numerous throttle valves is complex and expensive.

From the German patent specification DE 1 528 895 A centrifugal pump for conveying fluids is known in which, in addition to the centrifugal pump, a further auxiliary pump is arranged on the same drive shaft, the auxiliary pump serving to remove gas which escapes from the bubble or gas inclusions in a sludge-like liquid to be conveyed. A dedicated liquid / gas separator is not known from this application. A similar arrangement is shown in the EP 0478228B1 Described device for releasing gas from a liquid / solid mixture known. Also the German patent application DE 10 2006 016199 A1 describes a self-venting centrifugal pump in which, in addition to the centrifugal pump, a vacuum pump arranged on the same drive shaft is provided, which serves to discharge gas escaping from the liquid to be conveyed. This pump arrangement also has no dedicated separator. Out EP 0298949 B1 a similar pump unit is known. All four pumps of the prior art have in common that the centrifugal pump as the main pump for pumping liquid serves and the vacuum pump is provided as an auxiliary unit for removing the escaping gas.

In contrast, the German patent application DE 10 2007 013872 A1 describes a vacuum system for high amounts of additional liquid, in which the main pump is a vacuum pump and a feed pump arranged on the same drive shaft serves to discharge liquids which are to be separated from the gas conveyed by the vacuum pump. For this purpose, both the suction line and the outlet line of the vacuum pump each have two separators, which communicate with the suction and outlet lines of the fluid feed pump. However, due to the separators integrated in the intake and outlet lines, a quite large amount of space is required for such a vacuum system.

From the international patent application WO 2012/072601 a pump unit for a calibration tool of an extrusion system is known to the applicant, which has a separator which comprises a fluid inlet for a fluid mixture of liquid and gaseous media, a liquid outlet and a gas outlet. A vacuum pump with adjustable speed for generating a vacuum in the separator and a feed pump with adjustable speed for sucking off the liquid accumulated in the separator are each integrated directly into the separator. Furthermore, means for determining the level of the liquid in the separator are provided, which regulate the speed of the feed pump as a function of the level of the liquid in the separator via a control device. The end WO 2012/072601 Known pump unit is already very compact due to the integration of the vacuum pump and the feed pump. However, two separate pumps with their respective drives and control devices are still provided, the control devices having to be adapted to one another, since, for example, the delivery of the liquid from the separator with the feed pump influences the negative pressure in the separator, which in turn is controlled by the vacuum pump. However, such a complex pump unit with a correspondingly complex control system is not required for all applications.

In US 2178994 A . GB 463208 A and GB 2337561 A pumps in bearing support design are described, in which the vacuum pump and feed pump are arranged on a dedicated pump shaft. These feed pumps are conventional radial wheel pumps that tolerate only a small proportion of gas when pumping liquid / gas mixtures and therefore require a certain amount of liquid for operation, which completely covers the suction opening, so that pumping capacity is not guaranteed if the suction opening is not or only partially covered with liquid is.

The present invention is therefore based on the technical problem, starting from those from the international patent application WO 2012/072601 and the German patent application DE 10 2007 013872 A1 known pump units to provide an even more compact, simple and inexpensive pump unit for a calibration tool of an extrusion system.

This technical problem is solved by the pump unit according to the present claim 1. Advantageous developments of the invention are the subject of the dependent claims.

The present invention accordingly relates to a pump unit with a drive motor which has a motor shaft, a separator which has at least one fluid inlet for a fluid mixture which comprises liquid and gaseous media, at least one liquid outlet and at least one gas outlet, to a vacuum pump integrated in the separator Generation of a negative pressure in the separator, which communicates with the fluid inlet and the gas outlet, a pressure opening of the vacuum pump forming the gas outlet of the separator, a feed pump integrated in the separator for sucking off the liquid collected in the separator with an axial suction opening and an impeller, the are designed so that the feed pump acts as a liquid centrifuge, which can deliver liquid even when the suction opening is only partially covered with liquid, a pressure opening of the feed pump forming the liquid outlet of the separator, the vacuum uumpumpe and the feed pump are arranged on the common motor shaft of the drive motor. The negative pressure generated in the separator will also create a negative pressure in a calibration tool that is connected to the fluid inlet of the separator.

The integration of the vacuum pump in the separator means that the suction opening of the vacuum pump opens into the interior of the separator. Likewise, the integration of the feed pump in the separator means that the suction opening of the feed pump opens into the interior of the separator.

The fluid mixture sucked into the separator by the vacuum pump is separated in the separator, that is to say before the pump chamber of the vacuum pump has been reached, into a predominantly gas-containing phase and a predominantly liquid-containing phase. , The predominantly gas-containing phase is conveyed by the vacuum pump and the predominantly liquid-containing phase, which collects in the bottom area of the separator, is conveyed by the feed pump. The above Depending on the efficiency of the separator, the liquid that is transported away can of course contain more or less gas. Ultimately, the fluid sucked into the separator is separated into a gas portion and a fluid portion with depleted gas portion compared to the sucked fluid. For the sake of simplicity, however, the liquid which has been separated off is always mentioned below.

In contrast to that from the international patent application WO 2012/072601 Known pump unit, the pump unit according to the invention only has a drive motor that drives both the vacuum pump and the feed pump. The pump unit according to the invention is therefore less expensive to manufacture. The arrangement of both pumps on a common motor shaft also results in an even more compact design, since the separator can have a lower overall height.

In contrast to the other prior art mentioned at the outset, in the pump assembly according to the invention both the intake port of the vacuum pump and the intake port of the feed pump flow into the common separator, so that a particularly compact pump assembly is provided with simultaneous effective liquid separation.

In the pump unit according to the invention, the diameter of the suction mouth of the feed pump, which opens into the separator, is preferably larger by a factor of 2 to 3, particularly preferably about 2.5 times larger than the diameter of the suction mouth of a conventional feed pump, in particular a conventional centrifugal pump , A "conventional" pump design is to be understood here to mean a design in which the person skilled in the art orients itself on the known and typically used Pfleiderer design rules as used in the manual by Carl Pfleiderer, "The centrifugal pumps for liquids and gases", Springer -Verlag, 1961. A conventional centrifugal pump, for example, which should achieve a delivery volume of 6 cubic meters per hour, is designed with a suction mouth with a diameter of 35 mm. In contrast, a suction mouth with a diameter of 80 mm is provided in a pump unit according to the invention for the same delivery volume. In the pump unit according to the invention, it can thus be prevented that air gets into the impeller, which can lead to an interruption in the delivery flow. Put simply, it can be said that the feed pump provided according to the invention operates more as a liquid centrifuge than as a classic centrifugal pump.

The drive motor is preferably a drive motor with a controllable speed, so that the negative pressure prevailing in the separator and the flow rate of the liquid carried away from the separator by the feed pump can be controlled by changing the speed of the drive motor.

The impeller diameters of the vacuum pump and the feed pump are particularly preferably matched to one another. In the vacuum pump, the pressure difference generated is proportional to the square of the circumferential speed, i.e. to the square of the product of the speed and the outer diameter of the impeller. In the feed pump, the pressure difference is proportional to the product of the speed and the ratio of the outer diameter to the inner diameter of the impeller. Since both pumps are arranged on a common pump shaft according to the invention, the speed is the same in both cases. Depending on the desired pressure difference of the vacuum pump and the desired pressure difference of the feed pump, the respective impeller diameters can be adjusted accordingly.

Due to the arrangement of the feed pump and the vacuum pump on a common motor shaft, however, the adjustable vacuum and the delivery rate of the liquid to be removed can no longer be controlled independently of one another. The drive motor is therefore preferably regulated in such a way that a desired negative pressure is achieved in the separator. The pump unit according to the invention therefore particularly preferably comprises a pressure sensor which is arranged in the separator and which measures the pressure prevailing in the separator. The drive motor preferably comprises a control device which controls the speed of the drive motor as a function of the pressure determined by the pressure sensor. In particular, a setpoint of the desired pressure in the separator is specified in the control device and the regulation of the negative pressure prevailing in the separator is carried out by measuring the actual pressure in the separator by the pressure sensor and a corresponding regulation of the pressure to the setpoint by regulating the speed of the drive motor. The drive motor is then preferably an electric motor. To regulate the speed of the electric motor, the control device can in this case comprise a frequency converter with a PID controller. The control device can also include an integrated or external control panel by which the speed is set via a frequency converter with a PID controller.

Since the feed pump is arranged on the same motor shaft as the vacuum pump, the delivery capacity of the feed pump can no longer be changed by adjusting the speed independently of the speed of the vacuum pump. The feed pump is therefore preferably designed so that even at the lowest Speed of the drive motor, the resulting liquid can be reliably discharged. A centrifugal pump, which uses the centrifugal force to convey the liquid, is preferably used as the feed pump. The impeller of the feed pump is designed in such a way that the higher the liquid level in the separator, the more liquid the feed pump delivers. In contrast to conventional centrifugal pumps, such as radial pumps, in which the suction opening must be completely covered with liquid so that the suction flow does not stop, the impeller of the feed pump of the pump unit according to the invention is preferably designed so that the impeller can deliver even with a partially covered suction opening, or, if the level in the separator is below the suction opening, it can simply rotate freely.

In contrast to that, the pump unit according to the invention therefore requires WO 2012/072601 known pump unit also no longer a level sensor, and thus no second frequency converter and correspondingly complex cabling. This enables further cost savings to be realized. Nevertheless, a level sensor can be arranged in the separator as a kind of safety device, which, for example, switches off the customer unit in the event of a fault in the system. For example, a pressure sensor installed in the bottom and / or in the side wall of the separator can be used as the fill level sensor. Two pressure sensors are preferably used, the pressure sensor arranged in the upper region of the separator measuring the pressure in the gas space of the separator, while the pressure sensor arranged in the bottom region of the separator measures the total pressure from the pressure in the gas space and the pressure generated by the level of the liquid above the pressure sensor , so that the level above the pressure sensor can be calculated from the differential pressure. Of course, other devices for measuring the fill level can also be used, for example a strip arranged on the inner jacket of the separator with a plurality of conductivity sensors arranged one above the other can detect the transition from the liquid phase to the gas space.

The vacuum pump used to generate the vacuum is preferably a liquid ring vacuum pump, which is used in particular to produce a vacuum of less than 800 mbar absolute, or a side channel vacuum pump, which is preferably used to produce a vacuum of more than 800 mbar absolute.

Any liquid-gas separators known from the prior art can be used as separators. Are preferred in the pump unit according to the invention however, gravitational separators or separators that work on the cyclone principle are used.

The pump unit according to the invention can be used for a large number of applications in which a fluid mixture of gases and liquids must be separated into a phase essentially containing gases and a phase essentially containing liquids. However, the pump unit according to the invention is particularly preferably suitable for use with calibration tools in an extrusion system. For this purpose, the fluid inlet of the separator is preferably connected to a calibration tool of an extrusion system via a vacuum line.

Figur 1

eine perspektivische Ansicht des erfindungsgemäßen Pumpenaggregats;

Figur 2

eine Seitenansicht des erfindungsgemäßen Pumpenaggregats und

Figur 3

eine der Figur 2 im Wesentlichen entsprechende Seitenansicht mit Teilbereichen im Querschnitt.

The invention is explained below with reference to a preferred embodiment shown in the accompanying drawings. In the drawings:

Figure 1

a perspective view of the pump unit according to the invention;

Figure 2

a side view of the pump unit according to the invention and

Figure 3

one of the Figure 2 essentially corresponding side view with partial areas in cross section.

In Figure 1 A pump unit, designated overall by reference number 10, is shown in accordance with a preferred embodiment of the invention. The pump unit 10 comprises a separator 11, which in the example shown has two fluid inlets 12, 12a for a fluid mixture which comprises liquid and gaseous media, at least one liquid outlet 13 and at least one gas outlet 14. The fluid inlet 12, 12a can be connected via a vacuum line (not shown) to a calibration tool (also not shown) of an extrusion system (not shown). For a detailed description of such an extrusion system with one or more calibration tools, refer to the European patent application EP 0879132 A1 or the German utility model DE 20206606 U1 directed.

The pump unit according to the invention comprises a drive motor 15, which in the example shown is designed as an electric motor, which is controlled by a control device 16.

How to get the cross-sectional view of the Figure 3 can be seen, an impeller 18 of a vacuum pump 19 and an impeller 20 of a liquid feed pump 21 are arranged on a motor shaft 17 of the drive motor 15. The vacuum pump 19 has a suction opening 22 which opens into the interior of the separator 11 and thus communicates with the fluid inlet 12, 12a of the separator via the interior of the separator 11. A vacuum is generated in the separator 11 via the vacuum pump 19, so that a fluid mixture, for example a gas / water mixture, is drawn into the separator 11 by the calibration tool through the fluid inlet 12, 12a connected to the calibration tool. The liquid and gaseous media are largely separated in the separator 11. The separated gaseous media are transported via the suction opening 22 and the impeller 18 of the vacuum pump 19 into the pressure stage of the vacuum pump 19. How to get the representations of Figures 1 to 3 removes, the vacuum pump 19 is integrated in the separator, so that the pressure outlet of the vacuum pump 19 forms the gas outlet 14 of the separator.

In the lower area 23 of the separator 11, the liquid medium separated from the fluid mixture collects and is sucked off by the liquid feed pump 21. For this purpose, the feed pump 21 has an axial suction opening 24 which merges into the centrifugal impeller 20 of the feed pump 21. The feed pump 21 is also integrated into the housing of the separator 11 in such a way that the outlet opening of the pressure stage of the feed pump forms the liquid outlet 13 of the separator 11.

A vacuum sensor 26, which measures the pressure in the separator, is arranged in the head region 25 of the separator 11. The vacuum sensor 26 is connected to the control device 16, which controls the speed of the drive motor 15 via a frequency converter integrated in the control device 16 with a PID controller such that the negative pressure measured in the separator 11 largely corresponds to a predetermined target value. The control device also includes a control unit (not shown), via which the desired vacuum can be set. The control unit can be integrated into the control device 16 or can communicate wirelessly or as a cable with the frequency converter and the PID controller of the control device 16 as an external control unit.

The impeller 20 of the feed pump 21 is designed in such a way that liquid can be conveyed even if the axial suction opening 24 is only partially covered with liquid. If the liquid level in the separator 11 is even below the lower edge 27 of the suction opening 24, the feed pump can also rotate freely without problems. Depending on the respective application, the feed pump 21 is designed in such a way that, even at the lowest operating speed of the drive motor, all the liquid that is typically to be expected can be removed.

LIST OF REFERENCE NUMBERS

10

pump unit

11

separators

12

fluid inlet

12a

fluid inlet

13

liquid outlet

14

gas outlet

15

drive motor

16

control device

17

motor shaft

18

Vacuum pump impeller

19

vacuum pump

20

Delivery pump impeller

21

Liquid feed pump

22

Suction opening of the vacuum pump

23

lower area of the separator

24

axial suction opening of the liquid feed pump

25

Head area of the separator

26

vacuum sensor

27

Bottom edge of the suction opening

Claims (8)

1. Pump unit (10), with
   a drive motor (15) having a motor shaft (17),
   a separator (11) having at least one fluid inlet (12, 12a) for a fluid mixture comprising liquid and gaseous media, at least one liquid outlet (13) and at least one gas outlet (14),
   a vacuum pump (19) integrated into the separator (11) for generating a vacuum in the separator (11), which vacuum pump communicates with the fluid inlet (12, 12a) and the gas outlet (14), wherein a pressure opening of the vacuum pump (19) forms the gas outlet (14) of the separator (11),
   a conveying pump (21) integrated into the separator (11) for suctioning the fluid collected in the separator (11) with an axial suction opening (24) and an impeller (20), which are configured such that the conveying pump (21) acts as a liquid centrifuge, which can convey liquid even if the suction opening (24) is only covered in part with liquid, wherein a pressure opening of the conveying pump (21) forms the liquid outlet (13) of the separator (11),
   wherein the vacuum pump (19) and the conveying pump (21) are arranged on the common motor shaft (17) of the drive motor (15).
2. Pump unit according to claim 1, characterised in that the drive motor (15) is a drive motor with controllable rotational speed.
3. Pump unit according to claim 2, characterised in that a pressure sensor (26) is arranged in the separator (11).
4. Pump unit according to claim 3, characterised in that the drive motor (15) comprises a control device (16), which controls the rotational speed of the drive motor (15) depending on the pressure detected by the pressure sensor (26).
5. Pump unit according to any of claims 1 to 4, characterised in that the conveying pump (21) is a centrifugal pump.
6. Pump unit according to any of claims 1 to 5, characterised in that the vacuum pump (19) is a liquid-ring vacuum pump or a side-channel vacuum pump.
7. Pump unit according to any of claims 1 to 6, characterised in that the separator (11) is a gravity separator or a separator operating according to the cyclone principle.
8. Pump unit according to any of claims 1 to 7, characterised in that the fluid inlet (12, 12a) of the separator (11) can be connected with a calibrating tool of an extrusion system by way of a vacuum line.

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