Eccentric screw pump with magnetic coupling

Abstract

The invention relates to an eccentric screw pump (1) consisting of a rotor (2) with a pump drive shaft (5) rotating around a fixed axis in relation to a stator (3) in a bearing housing (4) driven by the motor drive shaft (6) of a motor (7), a power transmission line (8) and a carrier screw (9) moving in a rotary-oscillatory manner in the screw channel (10) of the stator (3); where the carrier screw (9) receives its drive torque via the power transmission line (8) and the power transmission line (8) compensates for the differences in the motion profiles of the carrier screw (9) and the pump drive shaft (5).An air gap (11) exists between the motor drive shaft (6) and the pump drive shaft (5), with the motor drive shaft (6) carrying a motor-side coupling half (12) and the pump drive shaft (5) carrying a pump-side coupling half (13); these coupling halves are connected to each other by means of magnetic forces to transmit torque through the air gap (11); furthermore, the air gap (11) is crossed by a sealing element (14) which hermetically separates the motor compartment (15) from the rest of the eccentric screw pump (1).

Description

TECHNICAL AREA

[0001] The present invention relates to a progressive cavity pump with a rotor consisting of a pump drive shaft rotating essentially around a fixed axis relative to a stator in a bearing housing. The pump drive shaft is driven by the motor drive shaft of a motor. The progressive cavity pump has a power train and a feed screw that rotates and oscillates within a screw thread of the stator. The feed screw receives its drive torque via the power train, which also compensates for differences in the movement patterns of the feed screw and the pump drive shaft. STATE OF THE ART

[0002] Eccentric screw pumps are known as such from the state of the art.

[0003] EP2944819B1 relates to an eccentric screw pump comprising a rotor extending along a rotor longitudinal axis from a drive end to a free end, a stator housing with an interior extending along the longitudinal axis from a stator inlet opening to a stator outlet opening and designed to accommodate the rotor, a drive motor with a drive shaft coupled to the rotor for transmitting torque, a first cardan joint inserted into the transmission of torque between the drive shaft and the rotor, and a stator outlet flange located downstream of the rotor in the direction of flow.

[0004] The motor-side end of the progressive cavity pump is sealed by a mechanical seal - as is regularly the case with progressive cavity pumps.

[0005] One disadvantage of this type of seal is that critical substances, and especially irritating or toxic substances, cannot be pumped, or only to a limited extent. Even when functioning correctly, mechanical seals always exhibit a certain degree of leakage – at least a small amount of the fluid being sealed enters the sealing gap, where it usually acts as a lubricant before evaporating and leaving the gap in gaseous form, thus giving the impression that the seal is perfectly tight.

[0006] DE 29 23 175 A1 describes a rotary pump.

[0007] US 2018 / 334891 A1, JP 6 941337 B2 and CN 105 221 418 A describe an eccentric screw pump with a magnetic drive coupling. UNDERLYING TASK

[0008] The object underlying the invention is to provide an eccentric screw pump that can also pump critical, in particular toxic, irritating or environmentally harmful fluids, without any risk of contamination or emissions. INVENTIONAL SOLUTION

[0009] The underlying problem is solved with an eccentric screw pump featuring a rotor consisting of a pump drive shaft that rotates essentially around a fixed axis relative to a stator within a bearing housing. This shaft is driven by the motor drive shaft of a motor. The pump drive shaft is connected via a power train to a screw conveyor, which rotates and oscillates within a screw thread of the stator. The screw conveyor receives its drive torque via the power train. Simultaneously, the power train compensates for differences in the motion of the screw conveyor and the pump drive shaft.

[0010] According to the invention, the progressive cavity pump is characterized by an air gap between the motor drive shaft and the pump drive shaft, and by the motor drive shaft carrying a motor-side coupling half and the pump drive shaft carrying a pump-side coupling half, which are connected to each other across the air gap by means of magnetic forces in a torque-transmitting manner. The air gap is penetrated by a seal that hermetically separates the motor area from the rest of the progressive cavity pump.

[0011] The motor drive shaft, i.e., the motor shaft used to drive the progressive cavity pump, and the pump drive shaft are not physically directly connected.

[0012] The gap between the motor-side coupling half and the pump-side coupling half, known as the air gap, can be filled with air or another medium, preferably the fluid being pumped. This medium should contain no or essentially no ferromagnetic material to avoid impeding the transmission of magnetic forces across the air gap. The air gap must be large enough to ensure that the two coupling halves of the magnetic coupling never come into contact with the seal spanning the air gap, even under the influence of vibrations or shocks. This prevents harmful frictional forces and mechanical wear.

[0013] The air gap is penetrated by the seal, for example in the form of a cylindrical air gap pot, in order to hermetically seal the motor area from the rest of the progressive cavity pump, so that the pumped fluid cannot enter the motor area.

[0014] The seal should contain no or essentially no ferromagnetic material in order not to impede the transmission of magnetic forces across the air gap and through the seal.

[0015] Another advantage of the progressive cavity pump designed according to the invention is that its seal towards the motor shaft is essentially wear-free even under the influence of abrasive media, which avoids or extends maintenance intervals and is beneficial to the service life.

[0016] Advantageously, the seal can be designed as a preferably cylindrical air gap pot, which is held with its open side on the bearing seat and forms a cavity projecting beyond the bearing seat, which accommodates the pump-side coupling half.

[0017] The cylindrical air gap pot has a cavity that accommodates the pump-side coupling half, allowing it to be arranged in a space-saving manner and enabling the inventive design to be mounted on existing bearing supports without requiring any major structural modifications. This allows conventional progressive cavity pumps to be easily equipped with the inventive design.

[0018] Advantageously, the motor-side and pump-side coupling halves are designed and magnetically equipped in such a way that they rotate synchronously with each other (during the trouble-free nominal operation of the progressive cavity pump), preferably without any slippage.

[0019] As soon as slippage occurs, high eddy currents are induced by the strong magnets of the two coupling halves of the magnetic coupling, which would thermally destroy the magnetic coupling quite quickly.

[0020] Advantageously, the progressive cavity pump can be equipped with a thermal sensor or, less preferably, with some other slip detector that triggers an alarm and / or takes measures to stop slipping as soon as slippage occurs between the coupling halves.

[0021] This ensures that the progressive cavity pump is not damaged by slippage-induced overheating in the coupling halves in the event of overload or even unintentional jamming of its progressive cavity screw. Advantageously, the pump-side coupling half can be cooled by the fluid pumped by the progressive cavity pump, ideally through direct contact. Advantageously, the pump drive shaft, preferably at its end face furthest from the screw, can carry a pumping element, better yet an impeller, ideally a centrifugal impeller, which drives a flow through the air gap.

[0022] This causes the pumping medium, such as the centrifugal pump impeller, to at least partially generate a flow through the air gap on the pump drive shaft, which can be used for cooling or flushing.

[0023] The flow through the air gap can be assisted by the pumping medium or essentially driven or generated solely by the pumping medium.

[0024] According to the invention, the pump drive shaft is mounted on rolling bearings, preferably in the bearing housing. Advantageously, but not falling within the scope of protection of the attached claims, the pump drive shaft can also be mounted on sliding bearings, preferably in the bearing housing.

[0025] Rolling bearings have the advantage that they allow fluid to flow more easily in a transverse direction, so that fluid can more easily reach or be carried away from the pump-side coupling half that needs to be cooled.

[0026] The rolling bearings can be designed as ceramic bearings, thus extending the service life and reducing maintenance compared to metallic bearings, especially under the influence of abrasive fluids.

[0027] Advantageously, a continuous, tube-like closed cooling channel can be provided, extending from the high-pressure area, preferably from the free end face of the screw conveyor, to an area of ​​the magnetic coupling, so that the higher pressure drives a flow of the pumped fluid from the high-pressure area into the area of ​​the magnetic coupling.

[0028] Through the cooling channel between the high-pressure area and the lower-pressure area of ​​the magnetic coupling, the pumped fluid is driven from the high-pressure area to the lower-pressure area of ​​the magnetic coupling, thus generating a cooling flow and / or a cleaning flow through the rotor, which prevents overheating of the magnetic coupling and therefore extends the service life of the progressive cavity pump.

[0029] The cooling channel can, for example, run through the entire rotor, comprising the pump drive shaft, power train, and auger, along an axis of symmetry, such as along the central longitudinal axis in the area of ​​the auger (which need not necessarily be straight). The cooling channel is produced either by means of a conventional drilling method through the entire rotor or by using a 3D printing process. In the 3D printing process, the entire rotor with the cooling channel running through it is printed using a 3D printer, and the material used for printing is sintered after printing to produce the rotor according to the invention.

[0030] Advantageously, the bearing support or drive area can have at least one connection through which an auxiliary fluid can be introduced. Preferably, it will have at least one further connection through which the auxiliary fluid can be discharged.

[0031] The two ports thus enable the introduction and discharge of auxiliary fluid into the drive area. This auxiliary fluid can, for example, be used to flush and clean the bearing housing or drive area and the magnetic coupling. When changing the pumped fluid or during maintenance work, the flushing and cleaning fluid is introduced through the first port and discharged through the second. Flushing the drive area may be necessary, for instance, to prevent significant sediment buildup caused by the pumped fluid within the drive area. Alternatively, the auxiliary fluid can also be used as an additional cooling fluid to further cool the drive area and the magnetic coupling.If prolonged plant downtime occurs due to a chemically highly aggressive pumped fluid, the auxiliary fluid can alternatively be a neutralizing agent introduced into the drive area to neutralize the remaining chemically highly aggressive pumped fluid in the drive area and thereby prevent damage from the fluid.

[0032] Advantageously, the auxiliary fluid-carrying area of ​​the bearing chair can be separated from the area carrying the fluid to be pumped by a contact seal.

[0033] This contact seal separates the area containing the auxiliary fluid from the area containing the fluid being pumped. This can be particularly advantageous when pumping toxic-abrasive or highly toxic products. The contact seal can be designed as a mechanical seal. Mechanical seals typically have a small leakage rate, so the non-abrasive and non-toxic flushing fluid only needs to remove this small amount of the fluid being pumped.

[0034] Advantageously, the auxiliary fluid can be supplied to and / or guided within the bearing chair or drive area in such a way that the bearing chair or drive area can be cleaned without disassembly.

[0035] This allows the drive area to be cleaned using auxiliary fluid for rinsing, without disassembling the progressive cavity pump.

[0036] Another aspect of the invention is an eccentric screw pump with a feed screw that is driven by the motor drive shaft of a motor and rotates and oscillates in a screw thread of the stator. The feed screw is directly connected to a pump-side coupling half and works together with a motor-side coupling half, the two coupling halves being connected to each other by means of magnetic forces across a permanently separating air gap (in the previously defined sense) in a torque-transmitting manner, and the air gap being designed and dimensioned such that it tolerates the rotating-oscillating movement that the feed screw imparts to the pump-side coupling half, preferably without contact.

[0037] One advantage of such a progressive cavity pump is that the screw is directly connected to the pump-side coupling half, eliminating the need for a power train or sliding or rolling bearings in the bearing housing to compensate for the screw's rotating-oscillating motion. This allows the progressive cavity pump to be designed much more compactly.

[0038] The air gap between the two coupling halves is designed and dimensioned to tolerate the rotating-oscillating movement of the screw conveyor. The eccentricity of this movement is therefore smaller than the width of the air gap, preventing contact and friction between the two coupling halves and the seal – which, for example, can again be in the form of a cylindrical air gap pot between the coupling halves.

[0039] Another advantage of this progressive cavity pump is that the magnetic coupling and its non-contact nature enable a completely new drive concept, because it is no longer necessary to connect the motor drive shaft to the wobbling screw conveyor in such a way that the motor drive shaft runs perfectly round.

[0040] Preferably, in this variant as well, the air gap can be penetrated by a seal that hermetically, preferably without contact, separates the motor area from the rest of the progressive cavity pump.

[0041] This hermetically seals the engine area, preventing the fluid being pumped from entering the engine area and thus preventing possible damage.

[0042] Preferably, this variant of the progressive cavity pump can include characteristic features of the progressive cavity pump described first above. Brief description of the drawings

[0043] The invention is explained with reference to the following drawings: Fig. 1 shows a representation of an eccentric screw pump; Fig. 2 shows a section of the eccentric screw pump made of Figure 1 Fig. 3 shows a cross-section of another embodiment of an eccentric screw pump, which is not part of the claimed invention; Fig. 4 shows a section of another embodiment according to the invention in cross-section. Examples of implementation

[0044] Figure 1Figure 1 shows a representation of an eccentric screw pump 1 with a rotor 2 consisting of a pump drive shaft 5 rotating essentially around a fixed axis relative to a stator 3 in a bearing holder. The rotor is driven by a motor drive shaft 6 of a motor 7. It is connected via a power train 8 to a screw conveyor 9, which rotates and oscillates in a screw thread 10 of the stator 3. The screw conveyor 9 receives its drive torque via the power train 8. Its function is to compensate for the differences in the motion of the screw conveyor 9 and the pump drive shaft 5.

[0045] An air gap 11 exists between the motor drive shaft 6 and the pump drive shaft 5. The motor drive shaft 6 carries a motor-side coupling half 12, and the pump drive shaft 5 carries a pump-side coupling half 13, which are connected to each other across the air gap 11 by means of magnetic forces, thus transmitting torque. The aforementioned air gap 11 is penetrated by a seal 14, which separates the motor section 15 of the motor 7 from the rest of the progressive cavity pump 1.

[0046] The seal 14 is designed as a cylindrical air gap pot, which is held at its open end against the bearing support. It forms a cavity projecting beyond the bearing support, which accommodates the pump-side coupling half 13. Thus, the air gap pot increases the installation space provided by the bearing support.

[0047] The motor-side coupling half 12 and the pump-side coupling half 13 are designed and magnetically equipped so that they rotate synchronously with each other during trouble-free operation of the progressive cavity pump 1.

[0048] A thermal sensor 16 or other slip detector is provided to detect slippage between the two coupling halves 12 and 13. If such slippage occurs, an alarm can be triggered and / or measures to stop the slippage can be initiated.

[0049] The progressive cavity pump 1 has a continuous, tubular, closed cooling channel extending from a first high-pressure area 18 to a second, lower-pressure area of ​​the magnetic coupling. The higher pressure drives a flow of the pumped fluid from the first high-pressure area to the second, lower-pressure area of ​​the magnetic coupling, thus generating a cooling and / or cleaning flow. The axis of symmetry 17 of the cooling channel is represented by a dash-dotted line.

[0050] Figure 2 shows a section of the eccentric screw pump 1 from Figure 1 , further comprising a centrifugal pump impeller 20, which serves as the pumping medium and drives the flow of the pumped fluid through the air gap 11. This allows the pump-side coupling half 13 to be cooled by the pumped fluid.

[0051] The pump drive shaft 5 is preferably supported on a first rolling bearing 21 and a second rolling bearing 22, wherein the rolling bearings 21 and 22 can be designed as ceramic bearings, thus extending the service life and reducing the maintenance effort compared to metallic bearings.

[0052] In a drive area 23, a first connection 24 is arranged through which an auxiliary fluid can be introduced, and a second connection 25 is arranged through which the auxiliary fluid can be discharged again to carry out a cleaning process. This allows the drive area to be cleaned without disassembly.

[0053] The two ports 24 and 25 can also be used to draw in the pumped fluid within the drive area to create an additional cooling flow.

[0054] Figure 3shows a cross-section of another embodiment of an eccentric screw pump 1, which is not part of the claimed invention, with a conveying screw 9 which is driven in a rotating manner by a motor drive shaft 6 of a motor, and which rotates and oscillates in a screw thread 10 of the stator 3.

[0055] The screw conveyor 9 is directly connected to a pump-side coupling half 13 without a power transmission link or any other intermediate element, such as a gimbal, to provide kinematic compensation. The latter interacts with a motor-side coupling half 12. The two coupling halves 12 and 13 are connected to each other by magnetic forces across a permanently separating air gap 11 (as defined above), thus transmitting torque. The air gap 11 is designed and dimensioned to tolerate the rotary-oscillating motion that the screw conveyor 9 imparts to the pump-side coupling half 13. The eccentricity of the rotary-oscillating motion is therefore smaller than the width of the air gap 11, preventing the air gap from locally dropping to zero.

[0056] The air gap is preferably penetrated by a seal 14 in the form of a cylindrical air gap pot. The motor area is then hermetically separated from the rest of the progressive cavity pump 1.

[0057] Figure 4 The figure also shows a section of another embodiment according to the invention in cross-section, in which a preferred arrangement of the individual parts can be seen in the cross-section of all parts. Reference symbol list

[0058] 1 Eccentric screw pump 2 Rotor 3 Stator 5 Pump drive shaft 6 Motor drive shaft 7 Motor 8 Powertrain 9 Conveyor screw 10 Screw thread 11 Air gap 12 Motor-side coupling half 13 Pump-side coupling half 14 Seal 15 Motor area 16 Thermal sensor 17 Axis of symmetry of the cooling channel 18 First high-pressure area 20 Centrifugal pump impeller 21 First rolling bearing 22 Second rolling bearing 23 Drive area 24 First connection 25 Second connection

Claims

1. Eccentric screw pump (1) with a rotor (2) formed by a pump drive shaft (5) rotating in a bearing block around a fixed axis relative to a stator (3), which is driven in rotation by a motor drive shaft (6) of a motor (7), a power train (8) and a feed screw (9) which circulates rotating-oscillatingly in a screw thread (10) of the stator (3), wherein the feed screw (9) receives its drive torque via the power train (8) and the power train (8) compensates for the differences in the movement sequences of the feed screw (9) and the pump drive shaft (5), wherein there is an air gap (11) between the motor drive shaft (6) and the pump drive shaft (5) , and that the motor drive shaft (6) carries a motorside coupling half (12) and the pump drive shaft (5) carries a pump-side coupling half (13), which are connected to each other via the air gap (11) by means of magnetic forces to transmit torque, wherein the air gap (11) is penetrated by a seal (14) which hermetically separates the motor area (15) from the rest of the eccentric screw pump (1), wherein the pump-side coupling half (13) is cooled by the fluid pumped by the eccentric screw pump (1), characterised in that the pump drive shaft (5) is mounted on roller bearings (21, 22), preferably in the bearing bracket, which can be flowed through in the transverse direction so that the fluid can reach or be removed from the pump-side coupling half (13) to be cooled.

2. Eccentric screw pump (1) according to claim 1, characterised in that the seal (14) is preferably designed as a cylindrical air gap pot, which is held with its open side on the bearing bracket and forms a cavity projecting beyond the bearing bracket, which accommodates the pump-side coupling half (13).

3. Eccentric screw pump (1) according to claim 1 or 2, characterised in that the motorside and pump-side coupling halves (12, 13) are designed and magnetically equipped in such a way that they rotate synchronously with each other during trouble-free operation of the eccentric screw pump (1).

4. Eccentric screw pump (1) according to claim 3, characterised in that the eccentric screw pump (1) comprises a thermal sensor (16) or other slip detector which triggers an alarm and / or takes measures to stop slippage as soon as slippage occurs between the coupling halves (12, 13).

5. Eccentric screw pump (1) according to one of the preceding claims, characterised in that the pump drive shaft (5), preferably at its end region facing away from the feed screw (9), carries a pump means, preferably a pump wheel, ideally a centrifugal pump wheel (20), which drives a flow through the air gap (11).

6. Eccentric screw pump (1) according to one of claims 1 to 5, characterised in that a continuous, tubular closed cooling channel (17) is provided, which extends from the high-pressure area (18) to an area (19) of the two coupling halves (12, 13) of the magnetic coupling with lower pressure, so that the higher pressure drives a flow of the pumped fluid from the high-pressure area (18) into the area (19) of the magnetic coupling.

7. Eccentric screw pump (1) according to one of the preceding claims, characterised in that the bearing block or drive area (23) has at least one connection (24) through which an auxiliary fluid can be introduced, and preferably has at least one further connection (25) through which the auxiliary fluid can be discharged again.

8. Eccentric screw pump (1) according to claim 7, characterised in that the auxiliary fluid-carrying area of the bearing block is separated from the fluid-carrying area by a contact seal.

9. Eccentric screw pump (1) according to claim 7 or 8, characterised in that the auxiliary fluid is supplied to the bearing bracket or drive area (23) and / or is guided therein in such a way that the bearing bracket or drive area (23) can be cleaned without dismantling.