WO2018014968A1

WO2018014968A1 - Centrifugal pump body mountable on a tank

Info

Publication number: WO2018014968A1
Application number: PCT/EP2016/067500
Authority: WO
Inventors: Werner RAFFEL; Hagen Renger
Original assignee: Egger Pumps Technology SA
Current assignee: Egger Pumps Technology SA
Priority date: 2016-07-22
Filing date: 2016-07-22
Publication date: 2018-01-25
Anticipated expiration: 2019-01-22

Abstract

The invention relates to a centrifugal pump body mountable on a tank (41) for producing a fluid flow through the tank (41), the pump body comprising an impeller (61) with a plurality of impeller vanes (65, 66, 67, 68, 69, 70) extending at a front face (76, 78) of the impeller (61 ) from a central hub (62) to an outer circumference (64, 75, 80) of the impeller, and a driving shaft (15) affixed to said central hub (62) such that a shaft/hub unit (30) extending along a rotation axis (20) of the impeller (61 ) is provided. The invention also relates to a centrifugal pump assembly comprising the pump body (1) and a tank (41). To provide the pump body with a high adaptability and availability with respect to a number of pumping tasks, the invention suggests that the impeller (61 ) is disposed inside a bottom casing (5) peripherally surrounding at least a lower portion of the outer circumference (64, 75, 80) of the impeller (61 ) and having a top sided aperture (16) through which the shaft/hub unit (30) passes along said rotation axis (20), wherein the bottom casing (5) is mountable to a floor (47) of the tank (41 ) below a bottom sided aperture of the tank (41 ) such that the shaft/hub unit (30) extends through an inner volume of the bottom casing (5) and an inner volume (42) of the tank (41 ), and wherein the bottom casing (5) has an outlet (8) for releasing the fluid flowing inside the bottom casing (5) toward the exterior.

Description

Centrifugal pump body mountable on a tank for producing a fluid flow through the tank and centrifugal pump assembly

The present invention relates to a centrifugal pump body mountable on a tank for producing a fluid flow through the tank. The pump body comprises an impeller with a plurality of impeller vanes extending at a front face of the impeller from a central hub to an outer circumference of the impeller. The pump body further comprises a driving shaft affixed to said central hub such that a shaft/hub unit extending along a rotation axis of the impeller is provided. The invention also relates to a centrifugal pump assembly comprising such a pump body and a tank.

Centrifugal pumps are often employed for pumping fluids comprising solid and/or gaseous additives. Such a fluid suspension may in particular include, besides a gaseous content, stringy material, material clusters and other objects tending to obstruct a fluid flow to be provided by such a pump. For instance, in the automotive industry a transport of fluids containing metallic or synthetic material clusters is regularly required in large amounts. When a centrifugal pump is operating under such conditions it is often necessary to reduce the solid parts to smaller pieces or to separate the additives from the fluid, in order to avoid material accumulations in front of the impeller and a clogging of the pump or obstructions of an outlet pipe. Frequently, residuals of those additives remain nevertheless and accumulate inside a container of the pumped fluid, i.e. inside a pump casing or fluid tank, such that the container must be cleaned after a certain time interval to ensure a proper functioning of the pump. A centrifugal pump body of the type mentioned above is provided in known centrifugal pumps, in particular for a pumping of fluid suspensions. An example is disclosed in international patent application No. PCT/CH2005/000337 to the same applicant. This pump comprises a successive arrangement of a fluid entrance, an impeller and a driving shaft inside a pump casing. The impeller comprises wide vanes extending in a forward chamber portion and a rearward chamber portion of an impeller chamber that is enlarged as compared to other pumps of that type. An outlet opening for the pumped fluid is provided in proximity to the fluid entrance at the top of the impel!er chamber.

The known pump arrangement can provide a significant improvement of the pump efficiency and an avoidance of pump failings stemming from gas inclusions in the pumped fluid. Nevertheless, it would be desirable to further improve the pump performance in various aspects including a further reduction of an undesired

concentration of solid material carried by the fluid within the pumping region and a resulting clogging risk. Also material accumulations inside the pump casing can be observed after a longer deployment of the pump with fluids having solid constituents, requiring a certain maintenance effort for a continuous usage. Another disadvantage of this pump is a quite low adaptability to varying requirements, such as the kind and amount of fluid to be delivered by the pump, which is mostly limited by a predetermined geometry and inner volume of the pump casing. In particular, the pump may not be applicable in an environment of rather low volume levels of the pumped fluid due to a rather high geometrical arrangement of the impeller and outlet. The low adaptability may also result in a low degree of availability of the pump in view of a rather time consuming preparation of the pump with respect to a new pumping environment or a time consuming exchange of the pump, for instance in case of a need of repairs.

It is an object of the present invention to remedy at least one of the above mentioned disadvantages and to provide the initially addressed centrifugal pump body and pump assembly with an improved adaptability and/or availability with respect to a number of subsequent or differing pumping tasks, in particular regarding a possibility of a fast and effortless installation of the pump to a given pumping environment, and a corresponding removal therefrom. It is a further object to allow a pumping operation even at comparatively small volume levels of a fluid to be delivered or in a situation in which large fluctuations of such volume levels may occur. It is yet another object to avoid material accumulations inside the tank even after longer intervals of pump operation of a fluid with solid constituents, in particular by also reducing or avoiding a risk of possible obstructions and/or by maintaining a high pumping efficiency. At least one of these objects is achieved by the centrifugal pump body according to claim 1 and the centrifugal pump assembly according to claim 12. The dependent claims define preferred embodiments.

Accordingly, the invention suggests that the impeller is disposed inside a bottom casing peripherally surrounding at least a lower portion of the outer circumference of the impeller and having a top sided aperture through which the shaft/hub unit passes along said rotation axis. The bottom casing is mountable to a floor of the tank below a bottom sided aperture of the tank such that the shaft/hub unit extends through an inner volume of the bottom casing and an inner volume of the tank. The bottom casing has an outlet for releasing the fluid flowing inside the bottom casing toward the exterior. In particular, the fluid to be released through the outlet is preferably flowing through the tank and through the bottom casing. On the one hand, a good adaptability and availability to altering pumping tasks can be made possible, for instance by mounting the bottom casing as required to a respective tank adapted to the specific task and to change the tank on which the bottom casing is to be mounted for a differing task, or by a quick mounting of a reserve unit in case of a need of repairs of a first unit. On the other hand, a pumping operation even at small volume levels of the fluid or during large volume fluctuations can be provided, in particular due to the arrangement of the impeller and also the outlet at the bottom casing situated below an inner volume of the tank such that even small filling levels of the tank are sufficient for a proper operation of the pump. Beyond that, an improved transport of additives in the fluid suspension can be expected due to this arrangement of the impeller and the outlet below the tank promoting a substantially complete evacuation of the tank, in particular without any undesired solid residues remaining inside the tank.

A centrifugal pump assembly according to the invention comprises such a pump body and a tank. Preferred features of the invention, as described below, can be

advantageously applied to the pump body and to the pump assembly according to the invention.

Preferably, the bottom casing is peripherally surrounding the outer circumference of the impeller at least along substantially the total height of the impeller vanes at the outer circumference. Preferably, the bottom casing comprises a side wall mountable below the inner volume of the tank and having an inner surface facing the outer impeller circumference. The inner side wall surface is preferably arranged at a close distance to the outer impeller circumference, or substantially bordering the same. In particular, the distance is preferably at most 20 mm, more preferred at most 10 mm, and most preferred notably less than 8 mm. In this way, an inner volume of bottom casing not covered by the impeller rotation is preferably kept small in order to optimize the pump performance. Also a risk of injury at the impeller edges is minimized. Preferably, the outlet is arranged at the side wall of the bottom casing. The outlet is preferably facing the outer circumference of the impeller. Such an arrangement of the outlet can advantageously contribute to a substantially complete evacuation of the tank. The outlet preferably comprises an exit hole for the fluid provided inside the side wall of the bottom casing. The outlet preferably further comprises a tube joined to the side wall of the bottom casing at an outer surface of the side wall and extending in a horizontal direction away from the side wall. In this way, a transport of the pumped fluid away from the pump body can be ensured in a convenient manner. Due to an arrangement of the outlet at a comparatively low height below the inner volume of the tank, in particular at a position facing the outer impeller circumference also located below the inner tank volume, a minimum depth of coverage by the fluid inside the tank, as required by classic centrifugal pumps, is not needed. Moreover, the bottom casing can be filled with the fluid from the tank substantially in an automatic and immediate manner due to its

arrangement below the tank, such that a pumping operation can take place anytime and substantially without any time delay.

Preferably, the bottom casing comprises a flange configured to be mounted to the floor of the tank. The mounting flange is preferably surrounding the top sided aperture. The flange is preferably protruding around an outer circumference of the bottom casing. This can facilitate the mounting and also un-mounting of the bottom casing from external. Preferably, a floor flange configured to be mating with the mounting flange is fixed to the floor of the tank. Preferably, the floor flange is surrounding the bottom sided aperture of the tank. The floor flange is preferably provided by a damping member, in particular by a rubber sealing, in order to provide a damping at the transitional region in between the bottom casing and the tank. Preferably, the mounting flange and the floor flange have a substantially equal outer diameter. Preferably, the inner diameter of the mounting flange is smaller as compared to the inner diameter of the floor flange. Preferably, a transfer plate is arranged above the impeller front face, the transfer plate being adapted to allow a passage of a fluid from the inner volume of the tank to the inner volume of the bottom casing. The top sided aperture through which the shaft/hub unit passes is preferably provided inside the transfer plate, in particular at a center portion of the transfer plate. The transfer plate preferably comprises at least one transfer aperture through which a fluid can enter an inner volume of the bottom casing from an inner volume of the tank. The transfer aperture is preferably provided at a radial distance from the top sided aperture surrounding the shaft/hub unit. More preferred, two transfer apertures are provided substantially equidistantly spaced from the top sided aperture. During installation of the pump body, the transfer plate is preferably adapted to be arranged in proximity to an upper end or substantially at an upper end of a lateral side wall of the bottom casing, in particular such that it constitutes a top wall of the bottom casing. Preferably, the transfer plate comprises a lower portion substantially matching to an inner diameter of the mounting flange and an upper portion substantially matching the inner diameter of the floor flange. Thus, the transfer plate is preferably adapted to be inserted into both the floor flange and the mounting flange, in particular from a position inside the inner volume of the tank. Due to a difference of the diameter of the lower portion of the transfer plate as compared to the upper portion of the transfer plate, an advantageous fixation of the transfer plate can be provided in between the floor flange and the mounting flange, in particular such that a correct position of the shaft hub/unit and the impeller can be ensured during mounting of the pump body. The shaft/hub unit is preferably supported by a sliding bearing. The sliding bearing is preferably provided inside the top sided aperture, through which the shaft/hub unit passes, or above said top sided aperture. The sliding bearing is preferably provided in the transfer plate. On the one hand, the sliding bearing may provide a statically indeterminate mount of shaft/hub unit. On the other hand, the sliding bearing can advantageously provide a compensation not only for the hydraulic forces acting on the shaft/hub unit but also for other forces caused by cutting operations which may in particular be performed by the impeller.

Preferably, the impeller vanes comprise at least one primary vane and at least one auxiliary vane. The primary vane preferably exhibits a larger height in the direction of the rotation axis than the auxiliary vane. More preferred, at least two primary vanes and at least two auxiliary vanes, and most preferred at least three primary vanes and at least three auxiliary vanes are provided. Preferably, the vanes are curved. Such an impeller geometry can advantageously contribute to an enhanced pump efficiency, in particular in combination with the above described vertical arrangement of the impeller and shaft/hub unit along a rotation axis substantially extending perpendicular to the ground surface. Preferably, the impeller vanes are also equipped to cut solid constituent parts contained in the fluid. To this end, at least one of the vanes is preferably equipped with an outer cutting edge at the outer circumference of the impeller, in particular a sharp cutting edge.

Preferably, the pump body further comprises a primary cutter. The primary cutter is preferably operative to cut larger solid constituents of a fluid suspension, for instance clusters of metal chippings, into smaller pieces. Thus, an obstruction of the transfer aperture and/or outlet by such constituents can be avoided. The primary cutter is preferably connected to the driving shaft, in particular in front of the impeller front face. Thus, the primary cutter is preferably located above the bottom casing, in particular above the transfer plate and substantially bordering an upper surface of the transfer plate. In this way, solid constituents of the fluid accumulated on this upper surface can be advantageously reached by the primary cutter. The transfer aperture in the transfer plate has preferably a size substantially only allowing the passage of solid constituents small enough, otherwise those constituents are chopped by primary cutter before their passage. The primary cutter preferably comprises two blades extending in radially opposed directions. Preferably, the blades are curved. The at least one transfer aperture preferably also exhibits a curved shape, in particular a kidney shape.

Preferably, the pump body further comprises a head part rigidly connected to the bottom casing. The head part is preferably mountable to the tank such that the head part is arranged above an upper face of the tank. The rigid connection between the head part and the bottom casing preferably comprises at least one connector member, more preferred at least two connector members, and most preferred at least three connector members. Preferably, at least one connector member, more preferred each connector member, extends substantially in parallel to the rotation axis of the impeller, in particular in parallel to the shaft/hub unit. Preferably, the connector member, in particular each connector member, is provided as a rod or a shaft. Preferably, a first end of the connector member is fixed to the head part and a second end of the connector member is fixed to the bottom casing. This construction has the advantage of being highly configurable, such that by an according choice of length for the respective connector member different heights of a tank can be accounted for. For instance, also quite little tanks with a comparatively small height can be equipped this way.

According to a first preferred tank configuration, the tank comprises a top sided aperture provided in an upper tank face. The top sided aperture of the tank has preferably a size allowing an insertion of at least the shaft/hub unit inside the inner volume of the tank during mounting of the pump body to the tank. According to a second preferred tank configuration, the upper face of the tank is substantially closed. Preferably, at least a through hole for the shaft/hub unit is provided in the upper tank face in both the first and second preferred configuration.

The head part of the pump body preferably comprises a top plate mountable to the upper tank face or being provided at the upper tank face. In the first preferred tank

configuration, the top plate preferably has a length exceeding a diameter of the top sided aperture provided in the upper tank face. Thus, the top plate can be preferably layed on the upper tank face and then, as required, provided with additional fixation means at the tank, for instance a screw connection at an upper border wall surrounding the top sided aperture of the tank. In this way, the mounting of the pump body can be facilitated.

Moreover, no direct connection, such as a screw connection, in between the head part and the bottom casing is preferably provided, in particular after mounting of the pump body to the tank. This can allow a fast and effortless mounting and un-mounting of the pump body, for instance even without the need of emptying the tank beforehand, in particular if the bottom casing is kept mounted the on tank floor. In this way, a high serviceability and also a high availability of the pump body can be provided. In particular, the pump body may thus be easily replaceable by a reserve unit, e.g. in case of a technical defect or the need of a technical revision. In the second preferred tank configuration, the top plate is preferably constituted by an integral constituent part of the tank, in particular by an upper wall of the tank by which the upper tank face is closed. Alternatively, the top plate is preferably provided in addition to an upper wall of the tank and can be disposed on top of the upper wall of the tank.

Preferably, at least one elastic member is arranged below the top plate, in particular at a lower surface of the top plate. After mounting of the pump body, the elastic member is preferably arranged in between the top plate and the upper tank face. After mounting of the pump body, the elastic member is preferably arranged next to a top sided aperture of the tank at the upper tank face. The top sided aperture is preferably surrounded by an upper border wall of the upper tank face on which the elastic member can be arranged. After mounting, the elastic member preferably extends around a closed path, in particular around the top sided aperture of the tank and in particular on top of the upper border wall. According to a preferred configuration, the elastic member is formed by an elastomer. Preferably, the shape of the elastic member substantially matches the shape of the top sided aperture of the tank. For instance, the top sided aperture may be circular and the closed path of the elastic member may be ring shaped or the top sided aperture may be rectangular and the closed path of the elastic member may be rectangularly shaped. Alternatively, at least two elastic members may be provided at opposed sides at the lower surface of the top plate. For instance, the top sided aperture may be rectangular and the elastic members may be arranged close to two opposed edges of the top sided aperture. The elastic member is preferably provided as a sealing for the top sided aperture of the tank. The elastic member can provide a certain length compensation for the pump body, in particular with respect to a tank height deviating from the distance between the top plate and the bottom housing. The top plate preferably also serves as a lid for the tank, besides its function as a mounting means of the pump body to the tank. This can contribute to an economization of component parts. The lid may in particular serve as a protection against an overflow of the tank. According to a preferred configuration, the top plate is provided with a tell-tale hole indicating a filling level of the tank.

The pump body preferably comprises a motor. The motor is preferably connected to the shaft/hub unit at a side of the shaft/hub unit opposing the impeller front face. The motor is preferably arranged above the head part, in particular above the top plate. Preferably, the motor is mounted on an upper surface of the top plate, in particular by a fixation flange disposed on the upper surface of the top plate. This can provide an additional protection for the motor in case of an overflow of the tank. Preferably, the motor comprises a motor shaft affixed to the driving shaft. Thus, the shaft/hub unit also comprises the motor shaft. The head part preferably comprises an aperture through which the shaft/hub unit passes.

Preferably, the tank floor comprises a tilted portion surrounding the bottom sided aperture. The tilted portion preferably exhibits an angle of inclination with respect to a virtual plane perpendicular to the rotation axis. The angle of inclination is preferably at least 20°, more preferred at least 30 " and most preferred at least 40°. The tilted portion can advantageously assist the intake of the fluid suspension from the inner tank volume toward the inner volume of the bottom casing, in particular through the transfer aperture at the transfer plate. Thus, in particular solid constituent parts tending to descend to the tank floor can be carried with the fluid along the tilted portion toward the upper surface of the transfer plate, such that they can be treated by the primary cutter and/or further descend to the bottom casing through the transfer aperture. Preferably, the tank is cylindrical, in particular it may have the shape of a circular cylinder or rectangular cylinder formed by its side walls. Preferably, the tank comprises a support for its placement on top of a ground surface. The support preferably protrudes from the tank floor. Thus, the tank floor is preferably spaced from the ground surface and the bottom casing, which is preferably arranged in between the tank floor and the ground surface. Preferably, the support is provided by a plurality of supporting legs. In particular, at least three supporting legs are preferably provided in the case of a circular cylindrical tank and at least four supporting legs in the case of a rectangular cylindrical tank.

Preferably, the pump body comprises two separate constituent parts to be mounted on the tank. This allows a rather easy installation and de-installation of the pump body on a tank and can thus contribute to a high availability of the pump body. Preferably, a first constituent part comprising the bottom casing is adapted to be mounted to the floor of the tank, in particular such that the top sided aperture of the bottom casing faces the bottom sided aperture of the tank. Preferably, a second constituent part comprising the shaft/hub unit is adapted to be put through the bottom sided aperture of the tank during its mounting. According to a first preferred implementation, the second constituent part is adapted to be inserted into the inner volume of the tank, in particular through a top sided aperture of the tank, and from the inner volume of the tank through the bottom sided aperture of the tank, in particular such that the impeller protrudes from the floor of the tank into a space corresponding to the inner volume of the bottom casing after mounting of the first constituent part. According to a second preferred implementation, the second constituent part is adapted to be inserted from below the tank floor into the bottom sided aperture in order to be mounted, in particular such that the impeller protrudes from the floor of the tank into a space corresponding to the inner volume of the bottom casing after mounting of the first constituent part. According to a third preferred implementation, the second constituent part is adapted for a mounting according to both of the above described first and second implementation.

Thus, the bottom sided aperture of the tank is preferably adapted to allow a passage of the second constituent part, in particular of the shaft/hub unit, during its mounting.

Moreover, a top sided aperture of the tank is preferably adapted to also allow a passage of the second constituent part, in particular the shaft/hub unit, during mounting.

Alternatively, the tank may be closed at its top side or a smaller size of the top sided aperture may be provided, when the second constituent part is mounted from a position below the tank through the bottom sided aperture. The second constituent part preferably comprises additional members of the pump body mounted to the shaft/hub unit, as described above, in particular at least one of the transfer plate, the primary cutter, and the impeller. Accordingly, the bottom sided aperture and/or the top sided aperture are preferably adapted to allow a passage of these components during mounting of the second constituent part.

The invention is explained in more detail hereinafter by means of preferred embodiments with reference to the drawings which illustrate further properties and advantages of the invention. The figures, the description, and the claims comprise numerous features in combination that one skilled in the art may also contemplate separately and use in further appropriate combinations. In the drawings: Fig. 1 is a perspective view of a centrifugal pump body;

Fig. 2 is a perspective view of a centrifugal pump assembly comprising the pump body shown in Fig. 1 ; Fig. 3 is a lateral sectional view of the pump assembly shown in Fig. 2; is a perspective view of an impeller; and Fig. 5 is a perspective view of a primary cutter.

Fig. 1 depicts a centrifugal pump body 1. Pump body 1 comprises a motor 2, a head part 3, a driving shaft 15, and a foot part 4. Foot part 4 comprises a bottom casing 5 in which an impeller is disposed. Driving shaft 15 interconnects a motor shaft of motor 2 with the impeller located inside bottom casing 5, in order to actuate a rotational movement of the impeller. To this end, driving shaft 15 substantially extends along a rotation axis 20 of the impeller. The impeller 61 is shown in Figs. 3 and 4, and further details with respect to impeller 61 are described below in conjunction with those figures.

Bottom casing 5 comprises a lateral side wall 7 provided by a substantially cylindrical body. Cylindrical body 7 has a substantially circular cylindrical shaped inner surface. This inner surface is surrounding an outer circumference of impeller 61 located therein. An outer surface of cylindrical body 7 has a fluted structure comprising lateral ribs 13 extending in parallel to driving shaft 15 in the axial direction 20. Bottom casing 5 comprises an outlet 8 with an exit hole 6 formed inside lateral side wail 7. Outlet 8 is connecting an inner volume of bottom casing 5 to the exterior. Outlet 8 further comprises an outlet tube 14 joined at one end to the outer surface of lateral side wall 7 around exit hole 6 provided therein. An opposed end of outlet tube 14 is free. The free end of outlet tube 14 is surrounded by a joint 9. The joint is provided as a connection flange 9 allowing its connection to another tube for an onward transportation of a fluid flowing out of outlet 8 through exit hole 6. Alternatively, joint 9 may be provided as a vitaulic coupling, a pipe thread, or any other tube connection known in the art. A bottom wall 11 is arranged at a lower side of bottom casing 5. Bottom wail 11 is provided by a solid plate fixed to a bottom edge of lateral side wall 7 such that the lower side of bottom casing 5 is substantially sealed in a fluid-tight manner. The fixation of bottom wail 11 to cylindrical body 7 is provided by a screw connection at the position of a lower end of lateral ribs 13 formed in the outer surface of cylindrical body 7. A transfer plate 12 is provided by a substantially circular disc adjoining a top edge of lateral side wall 7 and being fixed to side wall 7 in this position. In this way, transfer plate 12 forms a top wall of bottom casing 5 delimiting an inner volume of bottom casing with respect to an inner volume 42 of a tank 41 located above bottom casing 5. Transfer plate 12 comprises a central opening 16 defining a top sided aperture allowing a connection of driving shaft 15 to a central hub 62 of impeller 61 located inside bottom casing 5, as further described below in conjunction with Fig. 3. A shaft/hub unit 30 comprises the entity of driving shaft 15 and central hub 62. Around central opening 16, two substantially kidney-shaped openings 17, 18 are provided in the form of a respective cutting inside transfer plate 12. Kidney-shaped openings 17, 18 are located at a distance from the center of transfer plate 12, the distance corresponding to approximately half of the radius of transfer plate 12. Kidney-shaped openings 17, 18 define transfer apertures inside transfer plate 12 through which a fluid or fluid suspension can enter the inner volume of bottom casing 5 from outside, in particular from an inner volume of a tank located above. In this way, transfer plate 12 is adapted to allow a passage of a fluid from an inner volume of a tank to the inner volume of bottom casing 5. Above transfer plate 12, a primary cutter 25 is affixed to driving shaft 15. In this way, a rotational movement of primary cutter 25 around rotation axis 20 of impeller 61 located inside bottom casing 5 is actuated simultaneously with the actuation of the rotational movement of impeller 61. Primary cutter 25 comprises two blades 81 , 82 bordering an upper surface 19 of transfer plate 12. A mounting flange 21 circumferentially protrudes from the outer surface of lateral side wall 7. Mounting flange 21 is provided at an upper portion of bottom casing 5, more particularly at the upper edge of lateral side wall 7. Mounting flange 21 is substantially ring-shaped. Mounting flange 21 allows a mounting of bottom casing 5 to a tank floor, as illustrated in Figs. 2 and 3, in particular by a threaded or bolted connection in between mounting flange 21 and the tank floor. The external arrangement of mounting flange 21 , in particular outside an inner volume of bottom casing 5, facilitates a manual mounting and removal of bottom casing 5 to the tank floor.

Head part 3 comprises a top plate 31. Top plate 31 has a substantially rectangular shape, in particular square shape. Other shapes, such as an ovular or a circular shape, are also conceivable. The shape is adapted to substantially match an upper face of a tank in such a way that a top sided aperture 60 of a tank 41 can be covered by top plate 31 , in particular such that top plate 31 can be arranged on top of an upper border wall 46 of tank 41 surrounding top sided aperture 60. A side length of top plate 31 exceeds a diameter of bottom casing 5 including its widest section at mounting flange 21. On an upper surface 32 of top plate 31 , motor 2 is mounted. Motor 2 is fixed to top plate 31 at a fixation flange 34 by a screw connection. The diameter of fixation flange 34 may depend on the kind of motor 2. In the shown example, the diameter of fixation flange 34 substantially corresponds to the diameter of mounting flange 21. The diameter of fixation flange 34 may be larger than the diameter of mounting flange 21 when a different motor is used, for instance a motor with a comparatively large rotation speed, such as for instance 3600 rpm, and/or a smaller size of impeller 61 is required for the hydraulic actuation. On a lower surface 33 of top plate 31 , two elastic members 35, 36 are arranged. Elastic members 35, 36 are formed by a rubber material. Elastic members 35, 36 are strip-type and have a length substantially corresponding to a side length of top plate 31. Elastic members 35, 36 are disposed in proximity to two opposing lateral edges of lower surface 33 of top plate 31. At the respective position of elastic members 35, 36, fixation screws 38 are provided in top plate 31 for a fixation of elastic members 35, 36 in their desired position. Head part 3 is mountable to an upper tank face by laying down top plate 31 on top of the upper tank face at the position of elastic members 35, 36, as illustrated in Figs. 2 and 3. The weight of the constituent parts of pump body 1 mounted below head part 3 and the weight of motor 2 disposed on top may already provide a first fixation of these constituent parts at their correct position. An additional fixation by means of bolted or screw connections 38 in between top plate 31 and the upper tank face at the position of elastic members 35, 36 is then sufficient for a proper mounting of head part 3. Thus, no direct screw connection in between bottom casing 5 and the remaining part of pump body 1 is required for the mounting of pump body 1. It is noted that also other fixation methods of top plate 31 are conceivable. In particular, top plate 31 can be used as a lid for the tank, wherein conventional fixation methods for such a lid on a tank may be applied. In some situations, the weight of the constituent parts of pump body 1 connected to top plate 31 may be even sufficient for a proper fixation such that no other fixation means may be required. Head part 3 and bottom casing 5 are rigidly connected. The connection is provided by four connector members 28. The connector members are formed as connection rods 28. Each connection rod 28 extends substantially in parallel to driving shaft 15, thus also in parallel to common rotation axis 20 of impeller 61 and primary cutter 25. Connection rods 28 are equidistantly spaced from one another. Connection rods 28 are also equidistantiy spaced from driving shaft 15, in particular such that driving shaft 15 is in a center position with respect to surrounding connection rods 28. Connections rods 28 are mounted at their upper end to lower surface 33 of top plate 31 by a respective screw connection. Connections rods 28 are mounted at their lower end to upper surface 19 of transfer plate 12 of bottom casing 5 by another respective screw connection. The length of connection rods 28 substantially corresponds to the height of a tank volume of a tank on which pump body 1 is to be mounted, as illustrated in Figs. 2 and 3. Pump body 1 can be rather easily adapted to varying heights of a tank, on which pump body 1 is to be mounted, by a simple adjustment of the length of connection rods 28. A certain size tolerance for the length of connection rods 28 and a compensation for an inexactness of fabrication of the same can advantageously be provided by elastic members 35, 36.

Figs. 2 and 3 show a centrifugal pump assembly 40 comprising pump body 1 after mounting on a tank 41. Tank 41 is in particular adapted for the filling with a fluid suspension, for instance a fluid containing solid constituents such as remains or particles of a metallic or synthetic material, corresponding to a preferred application area of centrifugal pump body 1. The fluid suspension may also comprise gaseous content. In this context, tank 41 is referred to as fluid suspension tank. A preferred application field of pump body 1 is the pumping of such a fluid suspension.

Tank 41 comprises an inner volume 42 laterally delimited by a side wall 43. Side wall 43 substantially extends in parallel with respect to driving shaft 15 and rotation axis 20. Side wall 43 comprises four substantially square shaped lateral faces substantially arranged in the manner of a cube that is open at its top and bottom. A fluid suspension can enter inner volume 42 by an inlet 44. Inlet 44 is provided at one of the lateral faces at an upper portion of side wall 43. Tank 41 further comprises an upper face 45. Upper face 45 comprises an upper border wall 46 adjoining the upper edges of side wall 43 and surrounding a top sided aperture 60 of tank 41 located at the center. Upper border wall 46 has a perpendicular orientation with respect to side wall 43. Elastic members 35, 36 are adapted to be arranged close to two opposing edges of top sided tank aperture 60 during mounting of pump body 1 on tank 41 , such that they form a sealing of top sided tank aperture 60 after mounting. Alternatively, only one elastic member having a closed path may be provided on lower surface 33 of top plate 31. Thus, the elastic member can be arranged on upper face 45 such that its closed path substantially fully surrounds top sided tank aperture 60. In this way, the sealing of top sided tank aperture 60 can be further improved.

Tank 41 further comprises a floor 47. Floor 47 comprises a floor wall 48 adjoining the lower edges of side wall 43 and surrounding a bottom sided aperture 77 located at the center. Floor wall 48 comprises a tilted portion 49. Tilted portion 49 exhibits an angle of inclination with respect to a virtual plane perpendicular to rotation axis 20. In the shown example, the angle of inclination is about 10 °, wherein an angle of inclination of at least 20° is preferred, an angle of at least 30° is even more preferred, and an angle of at least 40° is most preferred. In this way, tilted portion 49 can be advantageously applied as a feeding slope assisting the intake of the fluid suspension through transfer apertures 17, 18 toward the inner volume of bottom casing 5. Thus, in particular solid constituent parts tending to descend to the tank floor can be carried with the fluid through transfer apertures 7, 18. Floor wall also comprises a flat portion 50 having a perpendicular orientation with respect to side wall 43. Flat portion 50 forms a radially inner part of floor wall 48 adjoining bottom sided tank aperture 77 at the center of floor 47 at its inner end. Tilted portion 49 forms a radially outer part of floor wall 48 adjoining flat portion 50 at its inner end and the lower edges of side wall 43 at its outer end.

A flange 55 is fixed to floor 47 below flat portion 50. Floor flange 55 is mating with mounting flange 21 such that it allows a fixation of bottom casing 5 below tank 41 . The fixation of floor flange 55 to floor wall 48 is provided by means of welding. Floor flange 55 may be formed by a rubber sealing providing a damping in order to reduce noise in between floor wall 48 and mounting flange 21. Floor flange 55 and mounting flange 21 have an equal outer diameter. The inner diameter of floor flange 55 is smaller than the inner diameter of mounting flange 21. Transfer plate 12 comprises a lower portion substantially matching the inner diameter of mounting flange 21 and an upper portion substantially matching the inner diameter of a floor flange 55. After mounting, transfer plate 12 is surrounded by floor flange 55 at its upper portion and mounting flange 21 at its lower portion in a fixed position due to the difference of the inner diameter of floor flange 55 and mounting flange 21. In this way, a correct position of transfer plate 12 and a corresponding correct position of shaft hub/unit 30 and impeller 61 can be ensured during mounting of the pump body.

Tank 41 also comprises a support 52 provided by four supporting legs. Supporting legs 52 are fixed to side waii 43, in particular in proximity to the lateral edges of its cubic arranged lateral faces. Each supporting leg 52 comprises a base 53 at its lower end for its placement on top of a ground surface. Supporting legs 52 protrude from floor 47 such that their bases 52 are spaced from floor 47. Inversely, floor 47 is spaced from the ground surface after placement of tank 41 on the ground surface. The spacing is useful for an installation of pump body 1 on tank 41 , in particular for arranging bottom casing 5 in between floor 47 and the ground surface, as further explained below.

Before the mounting of pump body 1 to tank 41 , pump body 1 is preferably provided in two separate parts. A first part comprises lateral side wall 7 and bottom wall 1 1 of bottom casing 5. A second part comprises the remaining constituent parts already assembled in one piece, in particular motor 2, head part 3, driving shaft 15, connections rods 28 and the remaining features of foot part 4 including primary cutter 25, impeller 61 , and transfer plate 12. In this way, a fast and effortless installation can be achieved. After placement of tank 41 on the ground surface, the first part of pump body 1 including lateral side wall 7 and bottom wall 1 1 of bottom casing 5 is mounted to floor 47 of tank 41 below bottom sided aperture 77 surrounded by floor wall 48. To this end, mounting flange 21 is fixed to floor flange 55 being fixed to flat portion 50 of floor wall 48 by means of a screwed or bolted connection 54, or less preferred by a rivet connection. Due to a comparatively small weight of the first part of pump body 1 , the firmness requirements of this connection may be low, such that an easily workable and removable connection type may be chosen, further contributing to a fast and effortless installation of pump body 1. For consistency reasons, it is noted that joint 9 of outlet 14 of lateral side wall 7 is not shown in Fig. 3.

In a subsequent step, the second part of pump body 1 is mounted. To this end, the remaining features of foot part 4, driving shaft 15, and connections rods 28 are inserted through top sided aperture 60 of tank 41 into inner volume 42 of tank 41 and then through bottom sided aperture 77 of tank 41 until impeller 61 is located at its correct position inside the inner volume of bottom wall 1 of pump body 1 and transfer plate 12 is located at the upper end of lateral side wall 7 of pump body 1 such that it is partially surrounded by mounting flange 21 around a lower portion and partially surrounded by floor flange 55 around a higher portion. At the same time, top plate 31 of pump body 1 is located on top of upper border wail 46 of tank 41 with elastic members 35, 36 arranged in between, wherein top plate 31 has a length extending exceeding a diameter of top sided aperture 47 of tank 41 . Bolted or screw connections 38 at those exceeding length portions above upper border wall 46 allow a fast and effortless mounting and also removal of pump body 1 . In the mounted state of pump body 1 on tank 41 , as shown in Fig. 3, it can be seen that central hub 62 of impeller 61 extends from below into top sided aperture 16 of bottom casing 5. Driving shaft 15 extends from above through bottom sided aperture 77 of tank 41 into top sided aperture 16 of bottom casing 5. Inside aperture 16 of bottom casing 5, a shaft-hub connection 58 in between driving shaft 15 and central hub 62 is provided. This geometry of impeller 61 and outlet 8 below inner volume 42 of tank 41 allows a pumping operation already at rather low filling levels of tank 41.

Motor 2 comprises a motor shaft 59 extending along rotation axis 20 for transmission of a rotational force. For this purpose, motor shaft 59 is fixed to driving shaft 15 via another shaft/hub connection 39. Driving shaft 15 comprises a cylindrical recess at an upper end opposing the end connected to central hub 62 of impeller 61 , which cylindrical recess constitutes a hub in which motor shaft 59 is inserted such that shaft/hub connection 39 is established. Shaft/hub connection 39 is fastened by a shrink disk 87 arranged around a conical reduction of the outer circumference at the upper end of driving shaft 15.

Shaft/hub unit 30 thus comprises the entity of driving shaft 15, motor shaft 59, and central hub 62 being interconnected by shaft/hub connections 39, 58. Head part 3 comprises a through passage aperture 22 located at a center portion of top plate 31. Driving shaft 15 extends from below into through passage aperture 22. Motor shaft 59 extends from above into through passage aperture 22. Inside through passage aperture 22, shaft-hub connection 39 between driving shaft 15 and motor shaft 59 is provided.

A sliding bearing 86 is arranged in between shaft/hub unit 30 and top sided aperture 16 inside transfer plate 12. This provision of sliding bearing 86 may result in a statically indeterminate mount of shaft/hub unit 30. However, sliding bearing 86 allows to provide a force balance not only for the hydraulic forces acting on shaft/hub unit 30 but also for other forces caused by cutting operations performed by primary cutter 25 and impeller 61 , which constitute an additional load acting on bearing 86. An internal bearing of motor 2 provides a further guidance for the actuation of shaft/hub unit 30 around rotation axis 20. Motor 2 is provided by a regular motor meeting a standard norm.

Fig. 4 depicts a detailed view of impeller 61. It is noted that other conceivable

configurations of an impeller corresponding to impeller 61 are disclosed in international patent application No. PCT/CH2005/000337, which is herewith included by reference, and can aiso be applied to an impeller in a pump according to the present invention without leaving the scope of the present invention. Impeller 61 comprises an impeller base 63 carrying a plurality of vanes 65 - 70 and central hub 62 it its center. Impeller base 63 is disc shaped. Central hub 62 comprises a cylindrical recess 79 at a free end 78 opposed to its end fixed to impeller base 63, in which recess 79 driving shaft 15 is inserted for establishing shaft/hub connection 58. Upper edges 76 of vanes 65 - 70, which are opposed to lower edges of vanes 65 - 70 fixed to impeller base 63, are free. The length of central hub 62 in the axial direction 20 exceeds the width of vanes 65 - 70 in the axial direction 20. Thus, free end 78 of central hub 62 as spaced from impeller base 63 at a larger distance than upper edges 76 of vanes 65 - 70. A front face of impeller 61 is thus defined by upper edges 76 of vanes 65 - 70 and/or free end 78 of central hub 62. As can be seen in Fig. 3, free front face 76, 78 of impeller 61 faces inner volume 42 of tank 41. Vanes 65 - 70 extend on top of impeller base 63 from central hub 62 to the periphery 64 of impeller base 63. Outer edges 75 of vanes 65 - 70 lead to outer circumference 64 of impeller base 63 from above. An outer circumference of impeller 61 at a lower portion of impeller 61 with respect to rotation axis 20 is thus delimited by the outer circumference 64 of impeller base 63. An outer circumference of impeller 61 at a middle portion of impeller 61 with respect to rotation axis 20 is thus delimited by outer edges 75 of vanes

65 - 70. An outer circumference of impeller 61 at an even higher portion of impeller 61 with respect to rotation axis 20 is thus delimited by an outer circumferential wall 80 of central hub 62. As can be seen in Fig. 3, bottom casing 5 is peripherally surrounding outer circumference 64, 75, 80 of impeller 61 substantially along the total height of impeller 61 with respect to rotation axis 20, including a lower portion around the outer circumference 64 of impeller base 63, a middle portion around outer edges 75 of vanes 65 - 70, and a higher portion around outer circumferential wall 80 of central hub 62.

Vanes 65 - 70 are curved. Their curvature runs along the rotation direction of impeller 61 around rotation axis 20. Vanes 65 - 70 comprise three primary vanes 65, 66, 67 having a larger height, thus covering a larger surface area, as compared to three auxiliary vanes 68, 69, 70 with a smaller height. Primary vanes 65, 66, 67 and auxiliary vanes 68, 69, 70 are alternately arranged around central hub 62, such that each primary vane 65, 66, 67 is neighbored by two auxiliary vanes 68, 69, 70, and vice versa. Primary vanes 65, 66, 67 and auxiliary vanes 68, 69, 70 are equidistantly spaced from one another.

Fig. 5 depicts a detailed view of primary cutter 25. Primary cutter comprises a

substantially ring shaped body 83 with a central aperture 84 in which driving shaft 15 is inserted. Blades 81 , 82 are joined to ring body 83 at two opposed lateral sides of its outer circumference. Blades 81 , 82 are curved. Their curvature runs against the rotation direction of impe!ier 61 around rotation axis 20. Primary cutter 25 is operative to cut larger solid constituents of a fluid suspension, for instance clusters of metal chippings, into smaller pieces in order to avoid an obstruction or a clogging of the fluid flow through aperture 17, 18 and outlet 8.

The purposes and functions of the arrangement of impeller 61 inside bottom casing 5 at a position under tank 41 according to the invention are plural. On the one hand, vanes 65 - 70 serve as a means to increase the pressure inside inner volume 42 of tank 41. On the other hand, vanes 65 - 70 serve as a cutting means, in particular to chop solid admixtures in the fluid to a smaller size. The cutting function is in particular achieved by comparatively sharp outer edges 75 of vanes 65 - 70. In addition, the described geometry of vanes 65 - 70 including primary vanes 65, 66, 67 with a larger height allow a pumping flow of a fluid containing a comparatively larger amount of gaseous admixtures as compared to conventional free flow pumps with a similar pumping arrangement. Moreover, an automatically induced degassing or air vent can be provided by the proposed arrangement of impeller 61 inside pump body 1 such that, when a breakaway of the fluid flow would occur due to a vast amount of a gas contained in the fluid, a substantially immediate continuation of the pumping flow will occur. The described geometry of impeller 61 is also advantageous for a centrifugal pump arrangement pumping liquids with solid or gaseous admixtures in that it allows, for instance, to reduce or prevent material accumulations and to increase the pump efficiency.

Overall, the above described pump assembly 40 is characterized in that bottom casing 5 is mountable to tank 41 such that bottom casing 5 and tank 41 can be provided as a single unit. Moreover, pump assembly 40 comprises pump body 1 exhibiting a successive arrangement of impeller 61 and shaft/hub unit 30 in a vertical direction, i.e. perpendicular to a ground surface and in particular such that rotation axis 20 has a perpendicular orientation with respect to the surface of the earth. Thus, as compared to other known centrifugal pumps, the direction of the impeller and shaft arrangement is rotated by about 180 °. This allows to provide an outlet for a fluid below the tank and permits the fluid not to be sucked out of the tank but to flow out from the tank.

Motor 2 and shaft/hub unit 30 are comprised in a pump body 1 forming a single unit and can be installed by inserting shaft/hub unit 30 through a top sided aperture 47 of tank 41 into inner volume 42 of tank 41 and from there into bottom casing 5 arranged below tank 41 , in particular in the manner of a pull-out design. Thereby, no direct screw connection is required in between a head part 3 of pump body 1 mountable on top of tank 41 and bottom casing 5. In particular, head part 3 comprises a top plate 31 which can be used as a lid for tank 41 and secured by conventional fixation methods. This allows a fast and effortless mounting and un-mounting of pump body 1 without the need of emptying tank 41 beforehand, if bottom casing 5 is kept mounted on tank floor 47. This in turn provides a high serviceability for pump assembly 40 and permits a high availability of pump body 1 , for instance by the provision of a reserve unit of pump body 1. Top plate 31 separates motor 2 from inner volume 42 of tank 41 such that motor 2 is protected even if an overfilling and overflow of tank 41 occurs. Another plate in between top plate 31 and motor 2 may be applied in terms of a second lid in order to achieve an even higher protection of motor 2 in such a situation. Top plate 31 may also be provided with a telltale hole indicating an overflow of tank 41. Another advantage of pump assembly 40 is the possibility to also realize quite little tanks having a comparatively small height. Pump body 1 is highly configurable and due to its variable way of construction, in particular with respect to a desired plunging depth of impeller 61 , literally each practical height of a tank can be realized. Thus, very precise customizations with respect to customer specifications can be realized. The operation of pump assembly 40 does further not require any elimination of air inside bottom casing 5. Bottom casing 5 is filled automatically with the medium to be pumped due to its arrangement below tank 41 such that a pumping operation can take place substantially without any time delay. Also a minimum depth of coverage by the medium, as required by classic centrifugal pumps, is not needed. Beyond that, the design of pump assembly 40 allows a substantially complete depletion or evacuation of tank 41 in the sense that no residues, in particular sold constituent parts, remain inside tank 41 . From the foregoing description, numerous modifications of the pump body and pump assembly according to the invention are apparent to one skilled in the art without leaving the scope of protection of the invention that is solely defined by the claims.

Claims

1. A centrifugal pump body mountable on a tank (41 ) for producing a fluid flow through the tank (41), the pump body comprising an impeller (61) with a plurality of impeller vanes (65, 66, 67, 68, 69, 70) extending at a front face (76, 78) of the impeller (61 ) from a central hub (62) to an outer circumference (64, 75, 80) of the impeller, and a driving shaft (15) affixed to said central hub (62) such that a shaft/hub unit (30) extending along a rotation axis (20) of the impeller (61 ) is provided, characterized in that the impeller (61) is disposed inside a bottom casing (5) peripherally surrounding at least a lower portion of the outer circumference (64, 75, 80) of the impeller (61 ) and having a top sided aperture (16) through which the shaft/hub unit (30) passes along said rotation axis (20), wherein the bottom casing (5) is mountable to a floor (47) of the tank (41 ) below a bottom sided aperture (77) of the tank (41) such that the shaft/hub unit (30) extends through an inner volume of the bottom casing (5) and an inner volume (42) of the tank (41 ), and wherein the bottom casing (5) has an outlet (8) for releasing the fluid flowing inside the bottom casing (5) toward the exterior.

2. The pump body according to claim 1 , characterized in that the bottom casing (5) comprises a mounting flange (21) surrounding said top sided aperture (16) and configured to be mounted to the floor (47) of the tank (41).

3. The pump body according to claim 1 or 2, characterized in that it further comprises a head part (3) rigidly connected to the bottom casing (5) and mountable to the tank (41 ) such that the head part (3) after its mounting is arranged above an upper face (45) of the tank (41 ).

4. The pump body according to claim 3, characterized in that said rigid connection between the head part (3) and the bottom casing (5) comprises at least one connector member (28) extending substantially in parallel to said rotation axis (20).

5. The pump body according to claim 3 or 4, characterized in that said head part (3) comprises a top plate (31) that can be arranged above said upper tank face (45), wherein the top plate (31 ) has a length exceeding a diameter of a top sided aperture (60) of the tank (41 ).

6. The pump body according to claim 5, characterized in that an elastic member (35, 36) is arranged below said top plate (31 ) such that the elastic member (35, 36) is arranged in between said top plate (31 ) and said upper tank face (45).

7. The pump body according to one of claims 1 to 6, characterized in that said shaft/hub unit (30) is supported by a sliding bearing (86).

8. The pump body according to one of claims 1 to 7, characterized in that it comprises two separate parts to be mounted on the tank (41), the first part comprising the bottom casing (5) and being adapted to be mounted to the floor of the tank (41 ), and the second part comprising the shaft/hub unit (30) and being adapted to be put through the bottom sided aperture (77) of the tank (41 ) during its mounting.

9. The pump body according to one of claims 1 to 8, characterized in that said impeller vanes (65, 66, 67, 68, 69, 70) comprise at least one primary vane (65, 66, 67) and at least one auxiliary vane (68, 69, 70), the primary vane (65, 66, 67) exhibiting a larger height in the direction of said rotation axis (20) than the auxiliary vane (68, 69, 70).

10. The pump body according to one of claims 1 to 9, characterized in that it further comprises a primary cutter (25) connected to the shaft/hub unit (30) in front of said impeller front face (76, 78).

11. The pump body according to claim 10, characterized in a transfer plate (12) is arranged above said impeller front face (76, 78), the transfer plate being adapted to allow a passage of a fluid from said inner volume (42) of the tank (41 ) to said inner volume of the bottom casing (5), wherein the primary cutter (25) is arranged above said transfer plate (12) and substantially bordering an upper surface (19) of said transfer plate (12).

12. A centrifugal pump assembly comprising a pump body (1 ) according to one of claims 1 to 11 and said tank (41 ).

13. The pump assembly according to claim 12, characterized in that said tank floor (47) comprises a tilted portion (49) surrounding said bottom sided aperture and exhibiting an angle of inclination with respect to a virtual plane perpendicular to said rotation axis (20).

14. The pump assembly according to claim 13, characterized in that said angle of inclination is at least 20°, more preferred at least 30° and most preferred at least 40°.

15. The pump assembly according to one of claims 12 to 14, characterized in that the tank (41 ) comprises a support (52) for its placement on top of a ground surface, wherein said support (52) protrudes from said tank floor (47) such that the tank floor (47) is spaced from the ground surface and said bottom casing (5) is arranged in between the tank floor (47) and the ground surface.