EP2535589B1 - Cutting assembly pump - Google Patents

Description

The invention relates to a centrifugal pump with a pump rotor, which is arranged in a housing, wherein before the influx of the medium in an impeller at least one cutting unit is arranged with a cutting surface and a rotating cutting body, wherein the cutting surface and cutting body axially in the direction of the axis of rotation of the cutting body with a contact force against each other are braced and the cutting surface has openings through which the medium flows.

In practice, there is often the problem that there are blockages when sewage with solid admixtures are conveyed through pipes with centrifugal pumps. To avoid this, cutting units are arranged before the medium flows into the centrifugal pump.

In this case, the cutting mechanism consists of a fixed part, the cutting surface and a rotating part, the cutting body. Depending on the application, circular, conical or cylindrical cutting surfaces can be used. The cutting surfaces have openings through which the medium flows. Therefore, the cutting surfaces are also sometimes referred to as a cutting screen. With a flat or conical shape of the cutting surface is called an insert. A cylindrical shape of the cutting surface is referred to as a cutting ring.

The rotating cutting body is arranged in front of and / or behind the cutting surface. He is also referred to as a cutting attachment.

While in all types of cutting the cutting action in the new state is good and thus the risk of clogging is low, the wear of the cutting edges leads to an increased tendency to clog. The main cause of wear is mineral or metallic admixtures in the waste water, which cause the leading edges of both the rotating and fixed parts to become dull. The running edges of the cutting unit are not affected by wear.

In the DE 20 2009 003 995 U1 such a cutting mechanism will be described. This device has no conveying properties. The comminution takes place by means of a cutting body which is designed as a knife rotor which rotates relative to a cutting surface designed as a cutting screen. The cutting body abuts axially in the direction of its axis of rotation on the cutting surface. Cutting body and cutting surface are braced against each other with a contact force, which is generated by a plurality of tension springs.

In the DE 25 36 555 A1 a device for pumping liquids will be described. Solid substances contained in the liquid are comminuted by the device. The comminution is not made by a cutting unit, but happens according to the principle described below. Through axial slots flows the loaded with solids liquid. The comminution takes place between a grinding element and an axially adjustable, stationary component, which is referred to in the document as a "stator". On a shaft above the grinding element, a centrifugal impeller is mounted, which has a downwardly directed outer wing surface. There is a close spacing between the downwardly directed wing surface and the upwardly directed stator surface. The incoming solid material is shattered there.

In the DE 2 313 403 describes an axial pump that can be used for pumping sludge or sewage. The crushing takes place in this pump also without the use of a cutting unit, but in that the blades of the impeller in a longitudinal blade extending blade-like edge end.

The DE 196 43 729 A1 describes a device which is preferably used for conveying manure. Through a supply line, a slurry flow is fed into a calming room. In the calming room, the slurry flow is diverted and enters an exit space. Between the calming room and the outlet room is a partition wall, wherein the slurry flow passes through a passage opening of the partition from the calming room in the outlet space. In the region of the partition wall, a cutting element which at least partially covers the passage opening is arranged. The cutting members of the cutting element are arranged on the side of the dividing wall facing the settling chamber, which forms the cutting unit together with the cutting element. The cutting element is biased by a spring element against the partition wall. As a result, a contact force between the cutting element and the partition wall is generated.

From the CA 2 030 881 A1 a waste water pump is known, which has a stationary cutting device and an axial cutting device and a radial cutting device, wherein axial cutting device and radial cutting device are arranged axially movable in front of an impeller on an impeller shaft. The Axialschneideinrichtung is urged by a coil spring in the direction of fixed cutting device.

The US 4,143,993 A discloses a submersible pump assembly for delivering sewage with an electric motor, a pump, and a housing having a suction port. Adjacent to the suction port, a crusher is disposed in the casing to chop sucked additives flowing through the suction port, the shredding device comprising a rotatable means for alternately retaining and rejecting the flow. The US 4,569,638 A1 shows a pump wherein a further axially directed force which assists the seating of the sealing surface is provided by the hydraulic forces exerted on the impeller.

Since blockages lead to failure of the conveyor system, the cutting unit must always be fully functional. For cutting units with flat or conical cutting surfaces, the functionality can be restored at least limited by adjusting the cutting gap between stationary and rotating part of the cutting unit. Cutter with cylindrical cutting surface must be completely renewed.

In cutting units cutting body and cutting surface are pressed against each other with a contact force. In this context, it is said in cutting machines that the cutting body and the cutting surface are braced against each other. In conventional cutters this contact pressure is generated by additional auxiliary equipment. Often this screw, plate or similar springs are used. Also clamping elements come on pneumatic or hydraulic basis for use. These separate auxiliary devices cause additional costs and also have the disadvantage that decreases with increasing operating time, the contact pressure between the cutting body and cutting surface. For example, feathers erode over time. In addition, due to the wear of the cutting body and cutting surface decreases the bias. Since the auxiliary devices are additionally used components, the susceptibility of the device also increases, since damage can also occur to these components. Another disadvantage is when starting the device. The contact pressure between the cutting body and the cutting surface must be overcome. For this purpose, motors are required, which generate a corresponding starting torque. In addition, to support the biasing force thrust bearings are required.

Object of the present invention is to provide a device that is inexpensive and has a low susceptibility. In this case, a high and durable cutting action should be guaranteed.

This object is achieved in that the contact pressure is generated due to the rotation of the pump rotor.

The pump rotor consists of the drive shaft with all components mounted on it. During operation of the centrifugal pump, all components of the pump rotor rotate. The components of the pump rotor include, among other things, the impeller and, in the case of a drive by means of an electric motor, the rotor of the electric motor.

According to the invention, the rotation of the pump rotor generates a contact force which acts axially in the direction of the axis of rotation of the cutting body. The forces can be generated axially in the direction of the motor, as well as in the opposite direction.

At standstill of the pump, this contact force does not work. Therefore, the motor does not have to overcome additional frictional forces when starting the cutting unit pump. It is required a lower starting torque, as opposed to conventional Devices, when starting no additional friction between cutting body and cutting surface occur.

Due to the rotation of the pump rotor thus a delivery pressure of the medium is generated. This is done according to the principle described below. The medium flows through the cutter and enters the rotating impeller of the centrifugal pump. There, the medium is accelerated by the rotating impeller on a circular path. Due to the effect of the centrifugal force, the medium flows from the axis of rotation radially outward into a collecting tube. In the impeller, the medium is brought to high speeds and thus has a high kinetic energy. The medium is braked in the manifold. A large part of the kinetic energy is converted into static pressure energy.

In a particularly advantageous embodiment of the invention, the delivery pressure of the medium presses the cutting surface against the cutting body. Preferably, the delivery pressure is passed to an annular piston. The cutting surface is arranged axially displaceable. The piston presses the cutting surface against the cutting body.

In another variant, the delivery pressure presses the cutting body against the cutting surface. For this purpose, the cutting body is preferably arranged axially displaceably on a piston. The delivery pressure generated due to the rotation of the pump rotor is transferred to the piston via a system of bores and grooves. In this way, the cutting body is pressed against the cutting surface.

Preferably, in the device according to the invention, the pump rotor and the cutting body are rotated together by a motor in rotation. It proves to be advantageous if the cutting body is connected to the drive shaft of the pump rotor, so that cutting body and pump rotor rotate at the same speed. In an advantageous variant of the invention, the cutting head is screwed to the drive shaft and / or the impeller for this purpose.

In a particularly favorable embodiment of the invention, the contact force between the cutting body and cutting surface is effected by an axial displacement of the pump rotor relative to the housing. The cutting head connected to the pump rotor presses on the cutting surface, whereby the contact force between the two arises.

Prerequisite is a storage that ensures axial mobility of the pump rotor. Only due to the rotation occurs an axial displacement of the pump rotor. When the pump is at a standstill, no contact force is applied.

The cause of the displacement is the axial thrust. Axial thrust refers to the resultant of all axial forces acting on the pump rotor. According to the invention, the cutting mechanism assumes the role of a thrust bearing for supporting the axial thrust. Thus, no additional thrust bearings are required in the device according to the invention, whereby costs are saved.

A variant for effecting an axial displacement of the pump rotor is that the impeller has a cover disk on one side and the axial displacement is produced in the direction of the opposite side on which the impeller is open or has a smaller cover disk. Characterized in that the impeller has a cover disc on one side and on the other side is open, or has a smaller cover plate, a hydraulic axial thrust is generated, which leads to an axial displacement of the pump rotor. According to the invention, the cutting body is connected to the pump rotor such that the cutting body presses on the cutting surface and in this way generates the contact force between the two.

Another variant for generating an axial displacement of the pump rotor is that the pump rotor is driven by an electric motor having an offset of the rotor to the stator. The rotor core is offset by a certain length axially to the stator. As a result, an electromagnetic train is generated, wherein the axial displacement counteracts the offset. This variant can be used either as a supplement or as an alternative to that described above. In an alternatively used variant, an impeller can be used, which is designed without cover plates and thus generates no or only a small hydraulic axial force.

In a particularly advantageous embodiment of the invention, the motor which drives the pump rotor, a control device is assigned, which can run at an interval in the opposite direction of rotation impeller and cutter body. Run the blades of the cutting head with a preset contact pressure against a cutting surface, while the running cutting edges of the knife and the cutting edge are sharpened while the leading edges wear out. The regular change of the direction of rotation ensures that the cutting ability is maintained.

When changing the direction of rotation, both the cutting head and the impeller of the centrifugal pump are driven in the opposite direction. In a particularly advantageous embodiment of the invention, the housing is formed as an annular space housing symmetrical to the discharge nozzle axis. In contrast to a spiral housing, a ring housing has a cross-section which remains constant along the circumference.

By using an impeller with purely radial blading and a symmetrical to the discharge nozzle axis ring housing a direction of rotation independent delivery characteristic is guaranteed. The direction of rotation-independent design of the centrifugal pump makes it possible to drive the pump rotor and cutter body with a common shaft.

Fig. 1

einen Axialschnitt einer Schneidwerkspumpe,

Fig. 2

eine Vorderansicht eines Schneidwerks,

Fig. 3

einen Radialschnitt des Laufrades,

Fig. 4

die Erzeugung der Anpresskraft durch elektromagnetischen Zug des Motors,

Fig. 5

die Erzeugung der Anpresskraft durch den hydraulischen Axialschub des Laufrades,

Fig. 6

eine Vorderansicht des Schneidwerks,

Fig. 7

einen Axialschnitt der Schneidwerkspumpe mit Erzeugung der Anpresskraft durch Wirkung des Förderdrucks auf die Schneidfläche,

Fig. 8

eine perspektivische Darstellung der in Fig. 7 dargestellten Variante,

Fig. 9

ein Axialschnitt der Schneidwerkspumpe mit Erzeugung der Anpresskraft durch Wirkung des Förderdrucks auf den Schneidkopf,

Fig. 10

eine perspektivische Darstellung der in Fig. 9 dargestellten Variante.

Further features and advantages of the invention will become apparent from the description of embodiments with reference to drawings and from the drawings themselves. It shows

Fig. 1

an axial section of a cutting unit pump,

Fig. 2

a front view of a cutting unit,

Fig. 3

a radial section of the impeller,

Fig. 4

the generation of the contact force by electromagnetic train of the engine,

Fig. 5

the generation of the contact force by the hydraulic axial thrust of the impeller,

Fig. 6

a front view of the cutting unit,

Fig. 7

an axial section of the cutting unit pump with generation of the contact pressure by the effect of the delivery pressure on the cutting surface,

Fig. 8

a perspective view of in Fig. 7 illustrated variant,

Fig. 9

an axial section of the cutting unit pump with generation of the contact pressure by the effect of the delivery pressure on the cutting head,

Fig. 10

a perspective view of in Fig. 9 illustrated variant.

Fig. 1 shows a centrifugal pump, in which in a housing 1, a pump rotor 2 is arranged. The pump rotor 2 includes, inter alia, an impeller 3, a drive shaft 4 and a rotor 5 of a motor 6. The centrifugal pump has a cutting unit 7, which is arranged in the impeller 3 before the inflow of the medium. The cutting unit 7 comprises a cutting surface 8 and a cutting body 9. In the embodiment, the cutting surface 8 is designed as a flat, circular cutting plate having openings 10 through which the medium flows. The cutting body 9 is arranged in the embodiment in front of the cutting surface 8, viewed in the flow direction of the medium.

According to the invention, a contact force F between the cutting body 9 and the cutting surface 8 is generated due to the rotation of the pump rotor 2. As a result, knives 11 of the cutting body 9 are pressed against the cutting surface 8.

The cutting surface 8 is fixedly connected to the suction cover 12 of the housing 1 and therefore does not rotate.

Centered in the direction of its axis of rotation of the cutting body 9 is provided with a bore. By means of a fastening element 13, preferably a screw, the cutting body 9 is connected to the impeller 3 and the drive shaft 4. According to the invention, a motor 6 rotates the pump rotor 2 and the cutting body 9 together. As a result, the cutting body 9 rotates at the same speed as the drive shaft 4 and the impeller. 3

In the exemplary embodiment, the rotation of the pump rotor 2 causes an axial displacement of the pump rotor 2 relative to the housing 1, whereby the contact force F of the cutting body 9 is generated on the cutting surface 8. The axial displacement of the pump rotor 2 is based on an axial thrust generated by the impeller 3. For this purpose, the impeller 3 in the embodiment, a suction-side cover plate 14 and is open to the pressure side. The axial displacement of the pump rotor 2 is generated in the direction of the opposite side of the cover plate 14, on which the impeller 3 is open. Characterized in that the impeller 3 is designed with suction side and motor side without cover plate 14, a hydraulic axial thrust arises, which points in the direction of the motor 6 and clamps the cutting unit 7.

The pump rotor 2 is mounted relative to the housing 1 by means of two radial bearings 15, 16. According to the invention, the cutting unit 7 acts as a thrust bearing and prevents contact between pump rotor 2 and housing 1. In the case of complete wear of the cutting unit 7, the rear radial bearing 16 serves as an emergency bearing by axial contact with the corresponding surface of the motor housing 17th

In all representations, the motor housing 17 is shown only schematically. The housing division required for mounting was not shown for reasons of clarity. The motor housing 17 surrounds the fixed stator 18 and the rotor 5 of the motor 6.

At the in Fig. 1 axial section shown are also the blades 19 of the impeller 3 to recognize their design in the description of Fig. 3 is carried out closer.

Fig. 2 shows a front view of a cutting unit 7. The cutting body 9, which is also referred to as a cutting head, comprises four purely radially extending wings 30. Each wing 30 is provided with a radially extending blade 11. The knives 11 of the cutting body 9 are pressed against the cutting surface 8.

As an alternative to using separate knives 11, the cutting body 9 can be designed so that the cutting edges are formed directly on both sides of the wings 30. Such variants are in the FIGS. 7 to 10 shown.

According to the invention, the pressing force required for pressing the cutting body 9 F is generated due to the rotation of the pump rotor 2. At standstill of the pump rotor 2 and thus the cutting body no contact force F. The contact force F acts axially in the direction of the axis of rotation of the cutting body 9. The cutting body 9 is connected by means of a fastening means 13 with the pump rotor 2.

The cutting surface 8 is designed in the embodiment as a flat, circular cutting plate and has openings 10 through which the medium flows. The openings 10 are distributed over the circumference of the cutting surface 8 in an inner and an outer ring. The blades 30 of the cutting body 9 overlap the openings 10 during rotation, the blades 11 running against the cutting surface 8 with a contact force. The running cutting edges of the blades 11 and the cutting surface 8 are sharpened, while the leading edges wear out.

A regular change of the direction of rotation ensures that the cutting ability is maintained.

According to the invention, the cutting body 9 is connected to the pump rotor 2. The motor 6 rotates the pump rotor 2 and the cutter body 9 together. Both rotate at the same speed. The motor 6 is associated with a control device which intermittently the pump rotor 2 with the cutting body 9 circulating in the opposite direction of rotation. Thus, the impeller 3 runs in different directions of rotation. In order to ensure a uniform delivery behavior, the centrifugal pump according to the invention has a rotational direction-independent conveying characteristic.

Fig. 3 shows that the housing 1 is formed as an annular space housing. It is formed symmetrically to the discharge nozzle axis 20. The impeller 3 is provided with a plurality of blades 19. The impeller 3 has a purely radial blading. Characterized in that the blades 19 extend in a purely radial direction and the housing is formed symmetrically to the discharge nozzle axis 20, the centrifugal pump has a characteristic independent of the direction of rotation.

Fig. 4 shows a variant in which the rotation of the pump rotor 2 causes an axial displacement of the pump rotor 2 relative to the housing 1. As a result, the contact force F of the cutting body 9 is generated on the cutting surface 8. At the in Fig. 4 illustrated variant, the axial displacement of the pump rotor 2 is effected by an electromagnetic train. The motor 6, which drives the pump rotor 2, is an electric motor with a stator 18 and a rotor 5. The stator 18 is also referred to as a stator pack. The rotor 5 is also referred to as rotor package. The rotor 5 has an offset L to the stator 18. As a result, an electromagnetic train is generated, which causes an axial displacement of the pump rotor 2. Since the cutting body 9 is connected to the pump rotor 2, this leads to a contact force between the cutting body 9 and cutting surface. 8

Fig. 5 shows a centrifugal pump with a front of the influx of medium into the impeller 3 arranged cutting unit 7. The cutting unit 7 has a fixed cutting surface 8, which is connected to the suction cover 12. In this exemplary embodiment, the rotating cutting body 9 is arranged behind the cutting surface 8, viewed in the flow direction of the medium. This arrangement of the cutting body behind the cutting plate is in Fig. 6 shown as a plan view. The medium with its solid components first flows through the openings 10. Thereafter a comminution of the solid components by the rotating cutting body 9 takes place, which sweeps over the openings 10 with its wings 19. Due to the rotation of the pump rotor 2, a contact force F between the cutting body 9 and the cutting surface 8, is generated. The cutting body 9 is connected to the pump rotor 2. The rotation of the pump rotor 2 causes an axial displacement of the pump rotor 2 relative to the housing 1, whereby the rotating cutting body 9 is pressed against the fixed cutting surface 8. The axial displacement of the pump rotor 2 is effected by hydraulic axial thrust, which acts counter to the flow direction. For this purpose, the impeller 3 on a pressure-side cover plate 14. The axial displacement takes place in the direction of the opposite side, at which the impeller 3 is open.

In the in the FIGS. 7 and 8th illustrated variant, a delivery pressure of the medium is built up due to the rotation of the pump rotor 2. Through the impeller 3 through holes 21 in the suction cover 12, the delivery pressure is passed to an annular piston 22, which presses the cutting surface 8 against the cutting body 9. The reaction forces are dissipated by the bearing 15 in the housing 1.

Fig. 8 shows the non-rotatable and simultaneously axially displaceable connection between suction cover 12 and cutting surface 8. The designed as a cutting plate cutting surface 8 is provided with molded lugs 23 which engage in grooves 24 in the suction cover 12. The desired axial preload force can be adjusted by dimensioning the annular piston 22 or by the radial position of the bore 21. It is also possible to replace the annular piston 22 by a plurality of evenly distributed over the circumference of individual pistons with associated bore system. Also, the bore system 21 can be replaced by a bypass line, which directs the delivery pressure from the housing 1 at a suitable location.

Fig. 9 and Fig. 10 show an arrangement for generating a hydraulic force for clamping the cutting body 9 against the cutting surface 8. In the variant shown in the two figures is due to the rotation of the pump rotor 2 constructed a delivery pressure of the medium. The delivery pressure presses the cutting body 9 against the cutting surface 8. In the cutting body 9 shown here, the cutting edges are integrally formed on the wings 19 of the cutting body 9. The cutting body 9 is arranged axially displaceable on a piston 26, wherein the contact force F is transmitted via the differential surface 27 on the cutting body 9. The necessary pressure is removed via a system of holes and grooves 28 from the rear wheel side space 29 between the impeller 3 and housing 1. In this case, the cutting body 9 is connected by the pin 25 with the impeller 3. The cutting plate 8 is firmly connected to the suction cover 12.

Claims (10)

1. Centrifugal pump having a pump impeller (2) which is arranged in a casing (1), at least one cutting unit (7) with a cutting face (8) and a rotating cutting body (9) being arranged in front of the inflow of the medium into an impeller wheel (3), the cutting face (8) and the cutting body (9) being braced against one another by way of a pressing force (F) axially in the direction of the rotational axis of the cutting body (9) and the cutting face (8) having openings (10), through which the medium flows, characterized in that the pressing force (F) is generated as a result of the rotation of the pump impeller (2).
2. Centrifugal pump according to Claim 1, characterized in that the pressing force (F) is generated by the fact that the delivery pressure of the medium presses the cutting face (8) against the cutting body (9).
3. Centrifugal pump according to Claim 1 or 2, characterized in that the pressing force (F) is generated by the fact that the delivery pressure of the medium presses the cutting body (9) against the cutting face (8).
4. Centrifugal pump according to Claim 1, 2 or 3, characterized in that the cutting body (9) is connected to the pump impeller (2), a motor (6) setting the pump impeller (2) and the cutting body (9) jointly in rotation.
5. Centrifugal pump according to one of Claims 1 to 4, characterized in that the rotation brings about an axial displacement of the pump impeller (2) with respect to the casing (1) and, as a result, generates the pressing force (F) of the cutting body (9) onto the cutting face (8).
6. Centrifugal pump according to Claim 5, characterized in that the impeller wheel (3) has a cover shroud (14) on one side and the axial displacement is generated in the direction of the opposite side, on which the impeller wheel (3) is open or has a smaller cover shroud.
7. Centrifugal pump according to Claim 5 or 6, characterized in that the pump impeller is driven by a motor (6) which has an offset (L) of the rotor (5) with respect to the stator (18), the axial displacement acting counter to the offset (L).
8. Centrifugal pump according to one of Claims 1 to 7, characterized in that the motor (6) is assigned a control device which lets the pump impeller (2) rotate with the cutting body (9) at intervals in the opposite rotational direction.
9. Centrifugal pump according to one of Claims 1 to 8, characterized in that the casing (1) is configured as an annular-space casing symmetrically with respect to the pressure-socket axis (20).
10. Centrifugal pump according to one of Claims 1 to 9, characterized in that the impeller wheel (3) has a purely radial blade system (19).

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