Pump component for a centrifugal pump assembly

Abstract

The present disclosure relates to a pump component (3a-c) for a centrifugal pump assembly (1), the pump component (3a-c) comprising - an impeller (24a-c), wherein the impeller (24a-c) comprises an axial suction inlet opening (19), wherein the impeller (24a-c) further comprises an axial bearing surface (51) circumferencing and sealing the axial suction inlet opening (19), - a pump shaft or pump shaft segment (25a-c) being rotatable about a shaft axis (z), wherein the pump shaft or pump shaft segment (25(a-c) comprises a radial bearing surface (55), and - an impeller connection (29a-c) for captively connecting the impeller (24a-c) with the pump shaft or pump shaft segment (25a-c) and transferring torque from the pump shaft or pump shaft segment (25a-c) to the impeller (24a-c) when the pump shaft or pump shaft segment (25a-c) rotates about the shaft axis (z), wherein the impeller connection (29a-c) allows a tilting motion of the impeller (24a-c) relative to the shaft axis (z).

Description

[0001] Title: Pump component for a centrifugal pump assembly

[0002] Description

[0003] TECHNICAL FIELD

[0004]

[0001] The present disclosure is directed to a pump component for a centrifugal pump assembly, in particular for vertical or horizontal multistage centrifugal pump assemblies.

[0005] BACKGROUND

[0006]

[0002] The shape and size of a pump assembly is designed to meet certain technical requirements and specifications. In particular, multistage centrifugal pumps like the pumps of the Grundfos CR series come in a wide range of sizes to cover a wide power range. The more pumping power is needed, the larger the pump is typically designed.

[0007]

[0003] Typically, such pumps comprise a rotor axis that may extend vertically or horizontally. An electric motor drives a rotor shaft extending along a rotor axis into a pump housing enclosing at least one impeller stage. A pump base typically provides a stand and / or a mounting bracket to fix the pump on a floor or to a wall. Inlet and outlet flanges for mounting the pump to a piping system may be part of the pump base and / or the pump housing. The pump housing is arranged between the motor and the pump base. The more pumping power or head is needed, the more impeller stages may be stacked along the rotor axis within the pump housing. Therefore, the axial length of the pump housing typically scales with the number of impeller stages. Depending on the maximum head the pump is supposed to be able to deliver, the radial extension of the impellers and the pump housing may be larger or smaller.

[0008]

[0004] EP 3 181 908 Al and EP 3 670 919 Al describe strap solutions to fix the motor stool to the pump base, so that the pump housing is securely sandwiched between the motor stool and the pump base due to the clamping tension force conveyed by the straps or tie rods.

[0009]

[0005] EP 4080058 Al discloses a centrifugal pump assembly with one or more impellers being fixed to or structurally integral with rotor shaft segments that are coupled to each other by a positive fit.

[0010]

[0006] A problem with the known solutions is that it is a challenge to implement both a radial bearing and an axial bearing for each impeller stage without demanding very strict manufacturing tolerances.

[0011] SUMMARY

[0012]

[0007] It is therefore an object of the present disclosure to provide a pump component for a centrifugal pump assembly that allows implementing both a radial bearing and an axial bearing for each impeller stage with less strict manufacturing tolerances.

[0013]

[0008] According to a first aspect of the present disclosure, a pump component for a centrifugal pump assembly is provided, the pump component comprising an impeller, wherein the impeller comprises an axial suction inlet opening, wherein the impeller further comprises an axial bearing surface circumferencing and sealing the axial suction inlet opening, a pump shaft or pump shaft segment being rotatable about a shaft axis, wherein the pump shaft or pump shaft segment comprises a radial bearing surface, and an impeller connection for captively connecting the impeller with the pump shaft or pump shaft segment and transferring torque from the pump shaft or pump shaft segment to the impeller when the pump shaft or pump shaft segment rotates about the shaft axis, wherein the impeller connection allows a tilting motion of the impeller relative to the shaft axis.

[0014]

[0009] So, the impeller connection provides a hinging or pivoting effect at a well-defined position between the impeller and the pump shaft or pump shaft segment. The impeller connection preferably defines a pivot point at a well-defined position along the shaft axis, wherein the tilting motion of the impeller relative to the shaft axis is allowed as a pivoting around the pivot point up to a certain maximum tilting angle, e.g. one degree. The impeller connection may, for example, be a flexure that adds angular compliance in rotational degrees of freedom about an axis perpendicular to the shaft axis.

[0015]

[0010] Optionally, the impeller connection may be loose or flexible to allow the tilting motion of the impeller relative to the shaft axis. If the impeller connection was rigid, the axial bearing surface of the impeller and the radial bearing surface of the pump shaft or pump shaft segment would define an over-constrained system that would have very strict manufacturing tolerances. This is, because both bearing surfaces restrict the same two rotational degrees of freedom, i.e. against a tilting motion relative to the shaft axis. It is preferably a loose or flexible impeller connection that allows the tilting motion of the impeller relative to the shaft axis, so that the pump component is not over-constrained and thus requires less strict manufacturing tolerances. The term “loose” shall mean herein that the impeller connection provides essentially no resistance against a tilting motion of the impeller relative to the shaft axis up to a certain maximum tilting angle, e.g. one degree. The term “flexi- ble” shall mean herein that the impeller connection provides a well-defined section between the impeller and the pump shaft or pump shaft segment, wherein said section is intentionally deformable against a resilient spring force to allow a tilting motion of the impeller relative to the shaft axis up to a certain maximum tilting angle, e.g. one degree. The resilient spring force is directed towards smaller tilt angles, and it is significantly smaller than a force that would be needed to non-intentionally deform the impeller or the pump shaft or pump shaft segment outside of the impeller connection. Thereby, neither the impeller nor the pump shaft or pump shaft segment is preferably deformable outside of the impeller connection. The impeller connection may, for example, be a flexure.

[0016]

[0011] It should be noted that “captively connecting” shall mean herein that the impeller and the pump shaft or pump shaft segment cannot be decoupled without damaging or destroying at least one of the group comprising: the impeller, the impeller connection, and the pump shaft or pump shaft segment.

[0017]

[0012] Optionally, the impeller connection may be integrally formed as one piece with the impeller. Alternatively, or preferably in addition, the impeller connection may be integrally formed as one piece with the pump shaft or pump shaft segment.

[0018]

[0013] The impeller connection may thus be a flexible part of the impeller and / or of the pump shaft or pump shaft segment. Alternatively, or in addition, the impeller connection may be a non-releasable positive form fit between the impeller and the pump shaft or pump shaft segment.

[0019]

[0014] Optionally, the impeller connection may be a bellows-shaped structure of the impeller and / or of the pump shaft or pump shaft seg- merit. The bellows-shaped structure may have some rotational deformation flexibility to allow for the tilting motion of the impeller relative to the shaft axis, and it may be rigid against translational deformation along the shaft axis and / or transverse to the shaft axis.

[0020]

[0015] Optionally, the impeller may be a separate structure from the pump shaft or pump shaft segment, wherein the impeller connection is a loose positive form fit between the impeller and the pump shaft or pump shaft segment, wherein the positive form fit allows the tilting motion of the impeller relative to the shaft axis. This embodiment is beneficial for using a non-segmented pump shaft.

[0021]

[0016] Optionally, the impeller connection may essentially not allow an axial or radial displacement of the impeller relative to the pump shaft or pump shaft segment. This is advantageous to keep the translational degrees of freedom restricted by the bearing surfaces, i.e. transverse to the shaft axis by the radial bearing surface and parallel to the shaft axis by the axial bearing surface.

[0022]

[0017] Optionally, the impeller connection may be a separate flexible element located between the impeller and the pump shaft or pump shaft segment. This embodiment is beneficial for using a non-seg- mented pump shaft.

[0023]

[0018] Optionally, the pump shaft or pump shaft segment may comprise a first axial end with a female connection and a second axial end with a male connection, wherein the female connection and the male connection are complementary to each other, such that a pump shaft or pump shaft segment of another one of said pump component is connectable to the pump shaft or pump shaft segment of said pump component transferring torque between the pump components. This is particularly beneficial if the pump shaft is segmented and each impeller stage comprises a pump shaft segment. The pump shaft segments of a plurality of pump components may be identical. If the pump comprises a certain number of impeller stages, it is advantageous that the pump comprises the same number of preferably identical pump components, each of which provides one impeller for each impeller stage.

[0024]

[0019] Optionally, the impeller may comprise two cover discs and impeller vanes arranged axially between the two cover discs, wherein the cover discs and / or the impeller vanes define a reference impeller wall thickness, wherein the impeller connection defines a connection wall thickness being smaller than the reference impeller wall thickness. The smaller connection wall thickness may be advantageous to provide for an added flexibility allowing the tilting motion of the impeller relative to the shaft axis.

[0025]

[0020] Optionally, the pump shaft or pump shaft segment may comprise an axial end with a female connection being connectable to a male connection at the other axial end of a pump shaft or pump shaft segment of another one of said pump component, wherein the female connection defines a reference shaft wall thickness, wherein the impeller connection defines a connection wall thickness being smaller than the reference shaft wall thickness. The smaller connection wall thickness may be advantageous to provide for an added flexibility allowing the tilting motion of the impeller relative to the shaft axis.

[0026]

[0021] Optionally, the axial bearing surface may be an annular surface being designated to face towards a pump base of the centrifugal pump assembly, and wherein the radial bearing surface is located at a shaft section of the pump shaft or pump shaft segment being designated to extend from the impeller towards a pump base of the centrifugal pump assembly. This is advantageous, because the impeller is, during pump operation, pressed axially towards the pump base of the centrifugal pump assembly. This is also beneficial for the axial bearing surface to act as a seal circumferencing and sealing the axial suction inlet opening.

[0027]

[0022] Optionally, the impeller connection comprises radial cams in a positive fit for torque transfer with the impeller. Preferably, the n > 2 cams are distributed in an n-fold rotational symmetry.

[0028]

[0023] Optionally, the cams have a convex outer contour in a plane parallel to the shaft axis. Such an outer contour may be beneficial for the two rotational degrees of freedom needed to allow for the tilting motion of the impeller relative to the shaft axis.

[0029]

[0024] Optionally, the impeller may have concave inner contours in a plane parallel to the shaft axis, each one of the concave inner contours being associated to one of the radial cams of the impeller connection, wherein each concave inner contour is complementary to the convex outer contour of the associated radial cam of the impeller connection. Such inner contours may be beneficial for the two rotational degrees of freedom needed to allow for the tilting motion of the impeller relative to the shaft axis.

[0030]

[0025] Optionally, the impeller, the pump shaft or pump shaft segment and the impeller connection may be additively manufactured in one manufacturing process. This is advantageous to manufacture the impeller with at least one inner cavity and the pump shaft or pump shaft segment being loosely “trapped” within said cavity of the impeller.

[0031]

[0026] Optionally, the impeller may define a central cavity having a first axial opening and a second axial opening having both a smaller crosssection than the central cavity, wherein the impeller connection comprises a cross-section that is larger than the cross-section of the first axial opening and second axial opening of the impeller, but equal to or smaller than the cross-section of the central cavity of the impeller. This is advantageous to loosely “trap” the pump shaft or pump shaft segment within said cavity of the impeller.

[0032]

[0027] Optionally, the impeller connection may be pressed through the first axial opening or the second axial opening of the impeller to expand radially into the central cavity of the impeller for being captively and loosely connected with the impeller.

[0033]

[0028] According to another aspect of the present disclosure, a centrifugal pump assembly is provided with one or more previously described pump components. The pump shaft of the pump assembly may be segmented or non-segmented. In case of a non-segmented pump shaft, the pump components share the non-segmented pump shaft and each pump component further provides an impeller connection and an impeller. In case of a segmented pump shaft, each pump component further provides a pump shaft segment, so that the pump shaft segments of the pump components connect to each other to establish the segmented pump shaft of the pump assembly.

[0034]

[0029] The pump shaft of the pump assembly as well as the pump housing may be segmented in a modular fashion, with one pump stage housing segment per pump stage, i.e. impeller. An absence of lengthdependent components is beneficial in terms of production cost, logistics und servicing, i.e. the pump length may be defined by the number of modules rather than a variety of components having an appropriate length. Given that the centrifugal pump assembly comprises n e N pump stages, i.e. pump components or impellers, there may be n + 1 or more pump shaft segments, at least one of which connects the motor with another one of a pump shaft segment of the pump components. Said pump shaft segment connecting the motor with another one of the pump shaft segments may be denoted as “motor shaft”. Each pump stage housing segment is preferably positioned axially between two of the impellers of the pump components, i.e. there may be n - 1 pump stage housing segments in case of n pump stages, i.e. pump components or impellers. Although the centrifugal pump assembly disclosed herein is preferably a multistage centrifugal pump assembly, i.e. n > 1 , it should be noted that in case of a single stage centrifugal pump assembly, i.e. n = 1, the pump stage housing segment may be integrated into the pump head, i.e. the pump stage housing segment may not be an extra part of the pump assembly. For n > 1, at least one of the pump shaft segments extends axially through a central opening in the pump stage housing segment(s) and is coupled to another pump shaft segment by a positive fit coupling for torque transfer.

[0035] SUMMARY OF THE DRAWINGS

[0036]

[0030] Embodiments of the present disclosure will now be described by way of example with reference to the following figures of which:

[0037] Fig. 1 shows an exploded view of an embodiment of a centrifugal pump assembly according to the present disclosure;

[0038] Figs. 2 shows a detail longitudinal cut view of a section of an embodiment of a centrifugal pump assembly according to the present disclosure;

[0039] Fig. 3 shows a perspective view of an embodiment of a pump component according to the present disclosure;

[0040] Fig. 4 shows a longitudinal cut view of the pump component shown in Fig. 3;

[0041] Figs. 5a-c show longitudinal cut views of different embodiments of an impeller connection having a bellows-shaped structure; Figs. 6a, b show different embodiments of the impeller connection for torque transfer; and

[0042] Fig. 7 shows a longitudinal cut view of an embodiment of the pump component that is suitable for a non-segmented pump shaft.

[0043] DETAILED DESCRIPTION

[0044]

[0031] Fig. 1 shows a centrifugal pump assembly 1 in form of a vertical multistage centrifugal pump assembly comprising a vertical shaft axis z and n = 3 pump stages, i.e. three pump components 3a-c having an impeller. The centrifugal pump assembly 1 comprises a pump base 5, three pump components 3a-c, two pump stage housing segments 7a, b, three sealing elements 9a-c and a pump head 1 1 , i.e. in total ten separate parts (without counting parts of a motor and motor control electronics). The number of parts of the centrifugal pump assembly 1 shown in Fig. 1 is significantly reduced compared to a conventional multistage centrifugal pump assembly comprising three pump stages. Except for the sealing elements 9a-c, one, some or all of the other seven parts shown in Fig. 1 are preferably additively manufactured.

[0045]

[0032] It should be noted that spatial terms like “upward”, “downward”, “upper” or “bottom” are used herein to facilitate the understanding of the invention in the context of the example of a vertical multistage centrifugal pump assembly 1 with a bottom pump base 5. However, the skilled person will readily understand that any other orientation of the shaft axis z, e.g. horizontal, may be applicable.

[0046]

[0033] The pump base 5 is an integral additively manufactured structure, preferably of a metallic material. The pump base 5 defines a pump inlet 13 and a pump outlet 15. The pump inlet 13 and the pump outlet 15 are arranged coaxially facing into opposite horizontal directions, so that the centrifugal pump assembly 1 may be installed into a straight pipe section. The pump base 5 further defines a stand structure with feet 17 standing on a floor or ground. The feet 17 comprise openings 18 for fastening the pump base 5 to the ground by means of fasteners, e.g. screws or bolts. An upper portion of the pump base 5 defines a reception structure for receiving the first pump component 3a. Said upper portion of the pump base 5 partly functions as a pump housing.

[0047]

[0034] The three identical pump components 3a-c each comprise an impeller 24a-c and a pump shaft segment 25a-c as will described in more detail with reference to Figs. 2-7. Each impeller 24a-c has a structure defining several impeller fluid channels extending from an axial (bottom) suction inlet opening 19 to a radial pressure outlet opening 21 . The suction inlet opening 1 faces towards the pump base 5, i.e. in Figs.

[0048] 1 and 2 downward (better visible in Fig. 3), and has an annular shape circumferencing the pump shaft segment. The radial pressure outlet opening 21 is directed radially outward. The radial pressure outlet opening 21 is positioned radially more outward than the suction inlet opening 19. The impeller fluid channels within the impeller 24a-c are separated from each other by impeller vanes 23. Furthermore, the pump components 3a-c each comprises, as a structure being integral with and / or captively connected with the impeller 24a-c, a pump shaft segment 25a-c extending predominantly in axial direction towards the pump base 5, i.e. downward. The pump shaft segment 25a of the first, i.e. bottommost, pump component 3a extends into a suction eye of the pump base 5. The pump shaft segments 25b, c of the other pump components 3b, c extend into the respective pump stage housing segments 7a, b positioned axially below the respective impeller 3b, c.

[0049]

[0035] A first pump stage housing segment 7a is arranged axially above the first pump component 3a, and a second pump stage housing segment 7b is arranged axially above the second pump component 3a. Both pump stage housing segments 7a, b are essentially identical in material and shape. They each comprise a first mechanical coupling 27 at a first axial segment end 29 facing towards the pump base 5 and a second mechanical coupling 31 at a second axial segment end 33 facing away from the pump base 5. The pump head 1 1 comprises an identical first mechanical coupling 27 at a (lower) pump head end 35 facing towards the pump base 5. Analogously, the pump base 5 comprises an identical second mechanical coupling 31 at an (upper) pump base end 37 facing towards the pump head 1 1 . The first mechanical coupling 27 is a male component of a bayonet coupling in form of radially outward rivet-like protrusions. In the shown example, there are twelve radially outward rivet-like protrusions evenly distributed circumferentially. The second mechanical coupling 31 is a corresponding female component of a bayonet coupling in form of hook-shaped slots at a radial inner side for receiving a head of a rivet-like protrusion of the first mechanical coupling 27. The first mechanical coupling 27 and the second mechanical coupling 31 are locked to each other by pushing the rivet-like protrusions axially into the hook-shaped slots up to a mechanical stop and a subsequent twist around the shaft axis z to move the rivet-like protrusions into a defined locking position.

[0050]

[0036] In the locking position, the first sealing element 9a is sealingly squeezed between the pump base 5 and the (lower) first axial segment end 29 of the (bottommost) first pump stage housing segment 7a. Analogously, the second sealing element 9b is sealingly squeezed between the first pump stage housing segment 7a and the (lower) first axial segment end 29 of the (topmost) second pump stage housing segment 7b. Finally, the third sealing element 9c is sealingly squeezed between the second pump stage housing segment 7b and the (lower) pump head end 35. Thereby, the fluid channels within the centrifugal pump assembly 1 are completely sealed to prevent leakage. As shown in Fig. 2, the pump stage housing segments 7a comprise a sealing groove 30 at the (lower) first axial segment end 29, wherein the sealing elements 9a-c are positioned at least partly within the sealing groove 30. The pump head 1 1 also comprises a sealing groove 30 (see Fig. 1 ) at the (lower) pump head end 35. Before coupling the pump stage housing segments 7a, b to each other or to the pump head 1 1 or pump base 5, the sealing elements 9a-c protrude at least partially radially outward out of the sealing groove 30. When the pump stage housing segments 7a, b are coupled to each other or to the pump head 1 1 or pump base 5, the sealing elements 9a-c are sealingly squeezed radially inward by a radial inner surface 32 of the other pump stage housing segment 7a, b or pump base 5. Alternatively, or in addition, the sealing elements 9a-c may be arranged to be squeezed axially between the components.

[0051]

[0037] Due to the twelve-fold rotational symmetry of the mechanical couplings 27, 31 , there are in principle twelve distinct rotational mounting positions which may serve as the locking position. However, it is preferable for a robust design to unambiguously define one of the twelve distinct rotational mounting positions as the only viable locking position. Preferably, each of the pump stage housing segments 7a, b comprises a twelve-fold rotational symmetry so that the twelve distinct rotational mounting positions may be indistinguishable from each other. This facilitates the assembly procedure and reduces the risk of incorrect assembling. A skilled person will readily understand that any m-fold rotational symmetry may be applicable to achieve this, wherein m > 2.

[0052]

[0038] Fig. 2 shows a detailed longitudinal cross-section of two impeller stages of the assembled pump assembly 1 of Fig. 1 . The pump components 3a, b each comprise a pump shaft segment 25a, b stacked into each other to form a segmented pump shaft extending along the shaft axis z. The pump components 3a, b each comprise an impeller 24a, b. Finally, the pump components 3a, b each comprise an impeller connection 39a, b for captively connecting the impeller 24a, b with the associated pump shaft segment 25a, b and transferring torque from the pump shaft segment 25a, b to the impeller 24a, b. In the embodiment shown in Fig. 2, the impeller 24a, b, is a separate structure from the pump shaft segment 25a, b, wherein the impeller connection 39a, b is a loose positive form fit between the impeller 24, b and the pump shaft segment 25a, b, wherein the positive form fit allows a tilting motion of the impeller 24a, b relative to the shaft axis z. The impeller connection 39a, b comprises radial cams 41 in a positive fit for torque transfer with the impeller 24a, b (shown in more detail in Figs. 4 and 6a, b). The cams 41 have a convex outer contour in a plane xz (paper plane in Figs. 2 and 4) parallel to the shaft axis z. The impeller 24a, b has concave inner contours 43, each one of the concave inner contours 43 being associated to one of the radial cams 41 of the impeller connection 39a, b. Each concave inner contour 43 is complementary to the convex outer contour of the associated radial cam 41 of the impeller connection 39a, b. The impeller 24a, b defines a central cavity 45 having a first (upper) axial opening 47 and a second (bottom) axial opening 49 having both a smaller crosssection than the central cavity 45. The impeller connection 39a, b with its cams 41 has a cross-section that is larger than the cross-section of the first (upper) axial opening 47 and second (bottom) axial opening 49 of the impeller 24a, b, but equal to or smaller than the cross-section of the central cavity 45 of the impeller 24a, b. Thereby, the pump shaft segment 25a, b is irrevocably “trapped”, i.e. captively connected, in the associated impeller 24a, b.

[0053]

[0039] It is important to note that each pump component 3a-c of Figs. 1 and 2 comprises an axial bearing surface 51 at the bottom surface of its impeller 24a-c. The axial bearing surface 51 circumferences and seals the (bottom) axial suction inlet opening 19. The axial bearing surface 51 has an annular shape and faces towards the pump base 5 of the centrifugal pump assembly 1 . The axial bearing surface 51 of the impeller 24a-c rests on a corresponding upward facing axial bearing surface 53 of the associated pump stage housing segment 7a, b.

[0040] It is further important to note that each pump component 3a-c of Figs. 1 and 2 comprises a radial bearing surface 55 at the radial outer surface of its pump shaft segment 25a-c. It should be noted that the radial bearing surface 55 may be provided by one or more rings that are pressed onto the pump shaft segment 25a-c. The radial bearing surface 55 is here located at a shaft section of the pump shaft segment 25a-c that extends from the impeller 24a-c (downward) towards the pump base 5 of the centrifugal pump assembly 1 . The radial bearing surface 55 of the impeller 24a-c is in sliding contact with a corresponding radially inward facing radial bearing surface 57 of the associated pump stage housing segment 7a, b. It should be noted that the corresponding radially inward facing radial bearing surface 57 may be provided by one or more rings that are pressed into the associated pump stage housing segment 7a, b.

[0054]

[0041] If the impeller connection 39a-c of each pump component 3a-c did not allow a tilting motion of the impeller 24a-c relative to the shaft axis z, the manufacturing tolerances for the impeller connection 39a-c would be very strict to meet the exact coaxial alignment of the corresponding axial and radial bearing surfaces 53, 57 of the associated pump stage housing segment 7a, b. The preferably loose or flexible impeller connection 39a-c of each pump component 3a-c, however, allows less strict tolerances for manufacturing the impeller connections 39a-c, preferably by an additive manufacturing method.

[0055]

[0042] The pump shaft segment 25a-c of the pump components 3a-c are stacked into each other to transfer torque from one pump component 3a, b to the next pump component 3b, c. Each pump shaft segment 25a-c therefore comprises a first (upper) axial end with a female connection 59 and a second (bottom) axial end with a male connection 61 , wherein the female connection 59 and the male connection 61 are complementary to each other, such that a pump shaft segment 25a-c of the subsequent (above) pump component 3a-c can be plugged into the pump shaft segment 25a-c of the previous (below) pump component 3a-c for transferring torque between the pump components 3a-c.

[0056]

[0043] Fig. 3 shows a perspective view of one of the pump components 3a-c alone. As can be seen, the impeller 24a-c of the pump component 3a-c comprises two cover discs 63 and impeller vanes 23 arranged axially between the two cover discs 63. It should be noted that the static pressure of the pumped fluid above the top cover disc is significantly larger than the static pressure of the pumped fluid at the axial suction inlet opening 19 below the impeller 24a-c. Thereby, the axial bearing surface 51 is pressed downward onto its corresponding axial bearing surface 53 of the associated pump stage housing segment

[0057] 7a, b (not shown in Fig. 3) for sealingly sliding on it. The impeller connection 39a-c is not visible in Fig. 3, but a largely exaggerated tilt angle 0 is shown between a tilted impeller axis z’ and the shaft axis z of the pump shaft segment 25a-c. In fact, the tilt angle 0 allowed by the impeller connection 39a-c is much smaller than displayed, preferably below one degree.

[0058]

[0044] Fig. 4 shows a longitudinal cross-section of the pump component 3a-c shown in Fig. 3. It clearly shows the female connection 59 in form of a hollow structure that is shaped complementary to the male connection 61 . The impeller connection 39a-c in form of a positive form fit between the cams 41 and the inner contour of the central cavity 45 of the impeller 24a-c captively connects the impeller 24a-c with the pump shaft segment 25a-c and transfers torque from the pump shaft segment 25a-c to the impeller 24a-c. The impeller connection 39a-c is here loose to allow for a certain tilting motion of the impeller 24a-c relative to the shaft axis z.

[0059]

[0045] Figs. 5a-c show different embodiments of the pump component 3a-c, wherein the impeller connection 39a-c is integrally formed as one piece with both the impeller 24a-c and the pump shaft segment 25a-c. Thus, the complete pump component 3o-c is formed os one piece in the embodiments shown in Figs. 5o-c. In these embodiments, the impeller connection 39o-c is not loose, but introduces a flexibility for allowing a certain tilting motion of the impeller 24a-c relative to the shaft axis z. This flexibility is added by a bellows-shaped structure between the impeller 24a-c and the pump shaft segment 25a-c. The impeller connection 39a-c is thus defined in these embodiments as the bellows-shaped structure between the impeller 24a-c and the pump shaft segment 25a- c. As shown in Figs. 5a, c, the bellows-shaped structure may be more part of the impeller 24a-c, and / or it may be more part of the pump shaft segment 25a-c as shown in Fig. 5b.

[0060]

[0046] The bellows-shaped structure has an impeller end 65, where the impeller connection 39a-c merges into the impeller 24a-c, and a pump shaft end 67, where the impeller connection 39a-c merges into the pump shaft segment 25a-c. In Figs. 5a, b, the bellows structure extends axially, so that the impeller end 65 has an axial distance to the pump shaft end 67. In Fig. 5c, the bellows structure extends radially, so that the impeller end 65 has a radial distance to the pump shaft end 67.

[0061]

[0047] The added flexibility is not only achieved here by the bellows- shaped structure itself, but also by a thinner wall thickness. As can be seen in Figs. 5a, c, compared to the cover discs 63 and / or the vane blades 23 defining a reference impeller wall thickness, the bellows- shaped impeller connection 39a-c has a connection wall thickness that is smaller than the reference impeller wall thickness. The reference impeller wall thickness may be defined at a location where the wall thickness of the cover discs 63 and / or the vane blades 23 is smallest.

[0062]

[0048] In the embodiment shown in Fig. 5b, the connection wall thickness is smaller than a reference shaft wall thickness being defined by the (upper) female connection 59 of the pump shaft segment 25a-c. This adds flexibility to allow for the certain tilting motion of the impeller 24a-c relative to the shaft axis z. Figs. 6a, b show different examples of how the impeller connection 39a- c may transfer torque from the pump shaft segment 25a-c to the impeller 24a-c. Fig. 6a shows a plurality of radial cams 41 that engage loosely, i.e. with some wiggle-room, into associated receptions 69 formed in the inner cavity 45 of the impeller 24a-c. Fig. 6b shows a perspective half-cut view of an impeller connection 39a-c in form of a cardan joint allowing the impeller 24a-c to rotate about a tilted impeller axis z’ being slightly tilted with respect to the shaft axis z (as shown in Fig. 3). It should be noted that the impeller connection 39a-c is preferably rotationally symmetric, e.g. 4-fold, with respect to the shaft axis z. Thereby, the cams 41 may be laterally guided by side walls 71 to have none or only very little wiggle room in the xy-plane perpendicular to the shaft axis z. This is beneficial to reduce noise and wear potentially induced by a lateral wiggle room in the xy-plane. A wiggle room along the shaft axis z is acceptable, because the impeller 24a-c is during pump operation hydrodynamically pressed downward onto the axial bearing surface 53 of the pump stage housing element 7a, b.

[0063]

[0049] Fig. 7 shows an embodiment of a pump component 3a-c that is applicable for a non-segmented shaft that is not shown in Fig. 7, but part of the pump component 3a-c. In this embodiment, the impeller connection 39a-c is here not integrally formed as part of the impeller 24a-c or of the pump shaft segment 25a-c. It is a separate item, preferably at least partly of different material, e.g. a polymer, with a lower Young modulus than the material of the impeller 24a-c, e.g. stainless steel. The impeller connection 39a-c is pressed axially through the first axial opening 47 or the second axial opening 49 of the impeller 24a-c to expand radially into the central cavity 45 of the impeller 24a-c for being captively and loosely connected with the impeller 24a-c. The non-segmented shaft can then protrude through the impeller connection 39a-c with positive form fit for torque transfer. One non-segmented shaft may be shared by two or more pump components 3a-c for establishing a multistage centrifugal pump assembly with a non-segmented shaft and several pump components 3a-c as shown in Fig. 7.

[0064]

[0050] Where, in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present disclosure, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the disclosure that are described as optional, preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims.

[0065]

[0051] The above embodiments are to be understood as illustrative examples of the disclosure. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. While at least one exemplary embodiment has been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art and may be changed without departing from the scope of the subject matter described herein, and this application is intended to cover any adaptations or variations of the specific embodiments discussed herein.

[0066]

[0052] In addition, "comprising" does not exclude other elements or steps, and "a" or "one" does not exclude a plural number. Furthermore, characteristics or steps which have been described with reference to one of the above exemplary embodiments may also be used in combination with other characteristics or steps of other exemplary embodiments described above. Method steps may be applied in any order or in parallel or may constitute a part or a more detailed version of another method step. It should be understood that there should be embodied within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of the contribution to the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the disclosure, which should be determined from the appended claims and their legal equivalents.

[0067]

[0053] List of reference numerals:

[0068] I centrifugal pump assembly 3a-c pump components

[0069] 5 pump base

[0070] 7a, b pump stage housing elements

[0071] 9a-c sealing elements

[0072] I I pump head

[0073] 13 pump inlet

[0074] 15 pump outlet

[0075] 17 feet

[0076] 18 openings

[0077] 19 impeller inlet

[0078] 21 impeller outlet

[0079] 23 impeller vanes

[0080] 24a-c impeller

[0081] 25a-d pump shaft segments

[0082] 27 first mechanical coupling

[0083] 29 first axial segment end

[0084] 30 sealing groove

[0085] 31 second mechanical coupling

[0086] 32 radial inner surface

[0087] 33 second axial segment end

[0088] 35 pump head end

[0089] 37 pump base end 39a-c impeller connection

[0090] 41 radial cams

[0091] 43 concave inner contours

[0092] 45 central cavity of impeller

[0093] 47 first axial opening of impeller

[0094] 49 second axial opening of impeller

[0095] 51 axial bearing surface of impeller

[0096] 53 axial bearing surface of pump stage housing element

[0097] 55 radial bearing surface of pump shaft or pump shaft segment

[0098] 57 radial bearing surface of pump stage housing element

[0099] 59 female connection of pump shaft segment

[0100] 61 male connection of pump shaft segment

[0101] 63 cover discs

[0102] 65 impeller end of impeller connection

[0103] 67 pump shaft end of impeller connection

[0104] 69 receptions formed in the inner cavity of the impeller

[0105] 71 side walls z shaft axis z’ tilted impeller axis e tilt angle

Claims

Claims1 . A pump component (3a-c) fora centrifugal pump assembly (1 ), the pump component (3a-c) comprising an impeller (24a-c), wherein the impeller (24a-c) comprises an axial suction inlet opening (19), wherein the impeller (24a-c) further comprises an axial bearing surface (51 ) circumferencing and sealing the axial suction inlet opening (1 ), a pump shaft or pump shaft segment (25a-c) being rotatable about a shaft axis (z), wherein the pump shaft or pump shaft segment (25(a-c) comprises a radial bearing surface (55), and an impeller connection (29a-c) for captively connecting the impeller (24a-c) with the pump shaft or pump shaft segment (25a- c) and transferring torque from the pump shaft or pump shaft segment (25a-c) to the impeller (24a-c) when the pump shaft or pump shaft segment (25a-c) rotates about the shaft axis (z), wherein the impeller connection(29a-c) allows a tilting motion of the impeller (24a-c) relative to the shaft axis (z).

2. The pump component (3a-c) according to claim 1 , wherein the impeller connection defines a pivot point at a well-defined position along the shaft axis, wherein the tilting motion of the impeller relative to the shaft axis is allowed as a pivoting around the pivot point.

3. The pump component (3a-c) according to claim 1 or 2, wherein the impeller connection(29a-c) is loose or flexible to allow the tilting motion of the impeller (24a-c) relative to the shaft axis (z).

4. The pump component (3a-c) according to any of the preceding claims, wherein the impeller connection (39a-c) is integrally formed as one piece with the impeller (24a-c).

5. The pump component (3a-c) according to any of the preceding claims, wherein the impeller connection (39a-c) is integrally formed as one piece with the pump shaft or pump shaft segment (25a-c).

6. The pump component (3a-c) according to any of the preceding claims, wherein the impeller connection (39a-c) is a bellows- shaped structure of the impeller (24a-c) and / or of the pump shaft or pump shaft segment (25a-c).

7. The pump component (3a-c) according to any of the claims 1 to 3, wherein the impeller (24a-c) is a separate structure from the pump shaft or pump shaft segment (25a-c), wherein the impeller connection (39a-c) is a loose positive form fit between the impeller (24a-c) and the pump shaft or pump shaft segment (25a-c), wherein the positive form fit allows the tilting motion of the impeller (24a-c) relative to the shaft axis (z).

8. The pump component (3a-c) according to any of the preceding claims, wherein the impeller connection (39a-c) does essentially not allow an axial or radial displacement of the impeller (24a-c) relative to the pump shaft or pump shaft segment (25a-c).

9. The pump component (3a-c) according to any of the preceding claims, wherein the impeller connection (39a-c) is a separate flexible element located between the impeller (24a-c) and the pump shaft or pump shaft segment (25a-c).

10. The pump component (3a-c) according to any of the preceding claims, wherein the pump shaft or pump shaft segment (25a-c) comprises a first axial end with a female connection (59) and a second axial end with a male connection (61 ), wherein the female connection (59) and the male connection (61 ) are complementary to each other, such that a pump shaft or pump shaft segment (25a-c) of another one of said pump component (3a-c) is connectable to the pump shaft or pump shaft segment (25a-c) of said pump component (3a-c) transferring torque between the pump components (3a-c).1 1. The pump component (3a-c) according to any of the preceding claims, wherein the impeller (24a-c) comprises two cover discs (63) and impeller vanes (23) arranged axially between the two cover discs (63), wherein the cover discs (63) and / or the impeller vanes (23) define a reference impeller wall thickness, wherein the impeller connection (39a-c) defines a connection wall thickness being smaller than the reference impeller wall thickness.

12. The pump component (3a-c) according to any of the preceding claims, wherein the pump shaft or pump shaft segment (25a-c) comprises an axial end with a female connection (59) being connectable to a male connection (61 ) at the other axial end of a pump shaft or pump shaft segment (25a-c) of another one of said pump component (3a-c), wherein the female connection (59) defines a reference shaft wall thickness, wherein the impeller connection (39a-c) defines a connection wall thickness being smaller than the reference shaft wall thickness.

13. The pump component (3a-c) according to any of the preceding claims, wherein the axial bearing surface (51 ) is an annular surface being designated to face towards a pump base (5) of the centrifugal pump assembly (1 ), and wherein the radial bearing surface (55) is located at a shaft section of the pump shaft or pump shaft segment (25a-c) being designated to extend from the impeller (24a-c) towards a pump base (5) of the centrifugal pump assembly (1 ).

14. The pump component (3a-c) according to any of the preceding claims, wherein the impeller connection (39a-c) comprises radial cams (41 ) in a positive fit for torque transfer with the impeller (24a- c).

15. The pump component (3a-c) according to claim 14, wherein the cams (41 ) have a convex outer contour in a plane (xz) parallel to the shaft axis (z).

16. The pump component (3a-c) according to claim 15, wherein the impeller (24a-c) has concave inner contours (43) in a plane (xz) parallel to the shaft axis (z), each one of the concave inner contours (43) being associated to one of the radial cams (41 ) of the impeller connection (39a-c), wherein each concave inner contour (43) is complementary to the convex outer contour of the associated radial cam (41 ) of the impeller connection (39a-c).

17. The pump component (3a-c) according to any of the preceding claims, wherein the impeller (24a-c), the pump shaft or pump shaft segment (25a-c) and the impeller connection (39a-c) are additively manufactured in one manufacturing process.

18. The pump component (3a-c) according to any of the preceding claims, wherein the impeller (24a-c) defines a central cavity (45) having a first axial opening (47) and a second axial opening (49) having both a smaller cross-section than the central cavity (45), wherein the impeller connection (439a-c) comprises a cross-section that is larger than the cross-section of the first axial opening (47) and second axial opening (49) of the impeller (24a-c), but equal to or smaller than the cross-section of the central cavity (45) of the impeller (24a-c).

19. The pump component (3a-c) according to claim 18, wherein the impeller connection (39a-c) is pressed through the first axial opening (47) or the second axial opening (49) of the impeller (24a-c) to expand radially into the central cavity (45) of the impeller (24a-c) for being captively and loosely connected with the impeller (24a- c).

20. A centrifugal pump assembly (1 ) with one or more pump components (3a-c) according to any of the preceding claims.

Images