DE102024116807A1 - centrifugal pump arrangement - Google Patents

Abstract

The invention relates to a centrifugal pump arrangement comprising an assembly (1) that includes a shaft (2) and a sleeve (3), wherein the sleeve (3) has a first region (4) with a functional surface (4a) and a closed cross-sectional profile, wherein a cavity (8) is formed in the region of the functional surface (4a) between the sleeve (3) and the shaft (2). According to the invention, the sleeve (3) has at least on one side of the first region (4) a second region (5) with an open cross-sectional profile having at least one slot (6).

Description

The invention relates to a centrifugal pump arrangement comprising a shaft and a sleeve, wherein the sleeve has a first area with a functional surface and a closed cross-sectional profile, wherein a cavity is formed in the area of the functional surface between the sleeve and the shaft.

The arrangement with a shaft and a sleeve can, for example, be designed as a shaft on which a shaft protection sleeve is arranged for protection. Furthermore, the arrangement can also be designed as a sliding bearing, in which the sleeve is designed as a sliding sleeve and is arranged on the shaft.

The shaft protection sleeve is mounted on the shaft and rotates, for example, in the bearing bushing. It protects the pump shaft from mechanical damage caused by shaft seals and bearing shells, and from chemical damage caused by aggressive pumped media.

It is known that shafts should not run directly in plain bearings and other constricted areas of the housing, but should be provided with shaft protection sleeves at such points where contact is possible.

The DE 23 34 673 A1 discloses a shaft protection sleeve consisting of a material that has a different coefficient of thermal expansion than the material of the shaft.

The DE 10 2022 106 442 A1 This relates to an arrangement for conveying hot liquids with a centrifugal pump, which has an impeller that is set in rotation by a shaft rotatably driven about a rotary axis, wherein the shaft is supported by at least one radial plain bearing and the plain bearing has at least one sleeve. The sleeve has an inclined surface at at least one end face, wherein the inclined surface acts on a corresponding inclined surface.

Plain bearings typically have a bearing gap that is usually parallel to the shaft axis. During operation, the bearing surfaces slide against each other, pressed together by hydraulic and/or mechanical forces. Between these two finely machined sliding surfaces is a bearing gap containing a lubricating film, usually liquid.

The arrangement with a shaft and a sleeve can, for example, be designed not only as a plain bearing but also as wear protection and features a shaft sleeve. Shaft sleeves can protect shafts from wear. If signs of wear appear, only the significantly less expensive shaft sleeve needs to be replaced, and not the entire shaft.

The DE 10 2015 221 255 A1 Disclosure reveals a shaft sealing arrangement. The arrangement comprises a pairing of a rotating element and a stationary element. A sealing gap for a lubricating film is formed between the two elements. The arrangement includes a shaft sleeve. The rotating element is formed integrally with the shaft sleeve.

Alternative designs are also known from the prior art. For example, the sleeve that protects the shaft can also be made of a non-metallic material. DE 10 2018 214 650 A1 This concerns a flow-guiding device. The device has a component that is made of or coated with a non-metallic material.

Alternative materials, in particular, have different coefficients of thermal expansion compared to metallic shafts. This usually leads, at high temperature differences between assembly and operating temperature, either to high thermally induced mechanical stresses within the shaft and/or the shaft sleeve, or to the shaft sleeve not having a secure connection to the shaft at operating temperature.

The object of the invention is to provide a centrifugal pump with an arrangement that exhibits as few thermally induced mechanical stresses as possible, or can be designed to be as free of thermally induced mechanical stresses as possible. The arrangement should be able to be securely joined and ensure a permanent connection between the shaft and sleeve, even at operating temperatures. Furthermore, the arrangement should be characterized by a compact design. The design of the arrangement should facilitate the replacement of spare parts. The arrangement should be simple and cost-effective to implement.

This problem is solved according to the invention by a centrifugal pump arrangement with an arrangement according to the features of claim 1. Preferred variants can be found in the dependent claims, the subclaims, the description and the drawings.

According to the invention, the sleeve has at least on one side of the first area or functional surface a second area with a open cross-sectional profile with at least one slot.

In an advantageous embodiment of the invention, the sleeve has an open cross-sectional profile with at least one slot on both sides of the functional surface or the first area.

The term "slit" refers to a cut, opening, or material recess made in a hollow body, i.e., the sleeve. This means the body's cross-section is no longer closed, but open due to the recesses.

An open cross-sectional profile refers to a specific shape or configuration of a cross-section that is open. Therefore, an open cross-sectional profile does not have a completely closed boundary or surface.

The functional surface describes the area of the sleeve that is subject to a particularly high degree of stress and thus relates to the area of the shaft that is protected by the sleeve. In the case of a sliding bearing function, the bearing surface is protected, and in the case of a sealing function, the sealing surface is protected. If the sleeve is used as wear protection, the functional surface protects the shaft underneath.

For example, at least one slot has an axial longitudinal extent. Thus, the material recess in the sleeve extends parallel to the axis of the shaft. The sleeve axis therefore corresponds to the orientation of the shaft axis.

In one variant of the invention, the slotting in the second area can be identical on both sides of the functional surface.

Alternatively, the slots in one second area can differ from the slots in the other second area.

The slots in the second area with an open cross-sectional profile form elastic sleeve sections, with the slots subdividing the cross-sectional profile into individual circular ring segments. These circular ring segments function as elastic elements that can accommodate the different expansion behavior of the sleeve and the shaft due to their different coefficients of thermal expansion in the form of bending.

In an alternative embodiment of the invention, the slots in the open cross-sectional profile can be configured differently on both sides of the functional surface. For example, the number, type, and design of the slots can differ.

In one variant of the invention, the open cross-sectional profile or the second area can have more than two, preferably more than four, in particular more than six slots.

For example, the slots can be identical in shape and design.

Alternatively, the slots in the cross-sectional profile can each have an individual design that differs from the other slots in shape and type.

For example, differently designed slots also each have an axial longitudinal extent.

In one embodiment of the invention, the at least one slot is oriented at an angle to a line parallel to the sleeve axis. This line lies, for example, in the same plane as the sleeve axis, and simultaneously in the same plane as the surface of the sleeve. The angle between the line parallel to the sleeve axis and the slot can be greater than 1° and less than 90°.

For example, the angle between the line parallel to the sleeve axis and the slot is more than 30° and less than 60°.

In one variant of the invention, the angle of the slot, viewed from a hypothetically unwound surface of the sleeve to an orthogonal line with respect to the end face of the sleeve surface, is more than 15° and less than 75°.

In a preferred embodiment of the invention, all angles of the slots in the open cross-sectional profile are identical.

For example, the angular alignment can have different angles for each slot.

In one variant, the slotting is corrugated. The corrugation can be S-shaped or sinusoidal and comprise one or more periods. The amplitude can be, for example, more than one and/or less than five times the sleeve wall thickness.

For example, the slot is formed at right angles to the surface of the sleeve. Thus, the slot extends parallel to the axis of the shaft on which the sleeve is mounted.

In an alternative version of the invention, the slot is inclined at an angle to the surface of the sleeve.

In the case of an angularly inclined design of the slot, the angle between a center line in a sectioned top view and a tangential line to the surface is more than 15° and less than 90°.

For example, the second area has a simply stepped slot.

In another variant of the invention, the second area has a multi-stage slotted design.

In the case of a multi-stepped slot, for example, the angle between a line parallel to the sleeve axis and the slot can be greater than 30° and less than 60°, while the angle between the steps is greater than 60° and less than 120°. The slot also extends parallel to the sleeve axis, including the steps.

For example, the slots are designed in a sawtooth shape, specifically as stepped slots.

For example, the slot has a width with a factor of more than 0.3 and less than 1.5 of the end-face sleeve wall thickness.

In one variant of the invention, the slot has a width with a factor of more than 0.7 and less than 1.2 of the end-face sleeve wall thickness.

For example, the recesses in the form of slots each have a length greater than a factor of 0.05 and less than 0.3 of the length of the sleeve.

In one variant of the invention, the outlet of the recesses is rounded.

The rounding can be formed as a partial circle or almost as a full circle as the end of the slot.

Alternatively, the outlet of the recess can be formed as a bore in the shaft protection sleeve. The rounded end of the slot provides advantageous protection against cracking due to high stresses in the shaft protection sleeve.

For example, the recesses extend beyond the ends resting on the shaft at least to the cavity of the sleeve. This effectively prevents the thermal induction of mechanical stresses in the sleeve, as the stresses can only occur in the contact area with the shaft due to the different coefficients of thermal expansion.

In one variant of the invention, the cavity is formed by piercing the sleeve.

Hollowing is a machining process used, for example, in cutting technology. A cavity is created between the shaft guard sleeve and the shaft by a machining operation, such as turning.

In another variant of the invention, the cavity is formed by cutting out the shaft.

In an alternative version of the invention, the cavity can be formed either by cutting out the sleeve or by cutting out the shaft.

For example, the shaft protection sleeve is made of a ceramic material.

In one variant of the invention, the shaft is made of a steel material.

By choosing two different materials for the sleeve and shaft, the functionality and service life of a plain bearing, for example, can be improved. The high-strength, wear-resistant ceramic sleeve, which has a lower coefficient of thermal expansion, protects the metal shaft, which is more susceptible to corrosion and less wear-resistant due to its higher coefficient of thermal expansion. The special design of the sleeve with an open cross-sectional profile reduces or eliminates mechanical stresses at the bearing surface of the sleeve on the shaft, as well as within the sleeve itself.

According to the invention, a centrifugal pump is used with an arrangement for reducing thermally induced mechanical stresses at high operating temperatures.

Ceramic materials generally exhibit a low coefficient of thermal expansion and good tribological properties. Combined with a low tendency to corrode, ceramic materials are in many cases ideally suited as sliding partners in medium-lubricated plain bearings in centrifugal pumps, where The housings and impellers are usually made of steel materials.

When ceramic materials are joined to steel materials, such as a shaft protection sleeve to a shaft, a component with a low coefficient of thermal expansion is brought into functional contact with a component with a significantly higher coefficient of thermal expansion. Particularly during temperature changes or when operating centrifugal pumps with high fluid temperatures, this can lead to impermissible thermal stresses or an undesirable fit gap.

According to the invention, the cross-sectional profile of the shaft protection sleeve is modified by slots in such a way that thermally induced mechanical stresses within the sleeve can be reduced to a permissible level and gaps in fit can be prevented.

For example, the shaft protection sleeve is designed with a functional surface that provides protection for the shaft. This functional surface has a closed cross-sectional profile. To reduce or prevent thermal stresses within the shaft protection sleeve, the closed cross-sectional profile is supplemented on both sides by an open cross-sectional profile.

Advantageously, this invention allows a shaft sleeve and a shaft made of materials with different coefficients of thermal expansion to be reliably joined, even under high-temperature conditions. Furthermore, material combinations with extremely different coefficients of expansion are also feasible. Stresses occurring in the shaft sleeve can also be limited or compensated for by the geometry of the elastic profile. This allows for a wide range of possible materials to be used for the shaft sleeve, particularly with regard to corrosion resistance and strength at elevated temperatures. Moreover, the shaft sleeve can be manufactured simply and cost-effectively.

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

• 1 eine perspektivische Draufsicht auf einen Wellenabschnitt mit Wellenschutzhülse,
• 2 einen Wellenabschnitt mit Wellenschutzhülse in einer Schnittdarstellung,
• 3 eine Schnittdarstellung des Wellenabschnitts im Bereich des offenen Querschnittsprofils,
• 4 eine Schnittdarstellung des Wellenabschnitts im Bereich der Funktionsfläche,
• 5 eine perspektivische Teildarstellung der Wellenschutzhülse,
• 6 eine perspektivische Teildarstellung einer weiteren Ausführung der Wellenschutzhülse,
• 7 eine perspektivische Teildarstellung einer alternativen Ausführung der Wellenschutzhülse,
• 8 eine perspektivische Teildarstellung einer weiteren alternativen Ausführung der Wellenschutzhülse,
• 9 eine perspektivische Teildarstellung einer weiteren alternativen Ausführung der Wellenschutzhülse,

This shows:

• 1 a perspective top view of a shaft section with a shaft protection sleeve,
• 2 a shaft section with shaft protection sleeve in a sectional view
• 3 a sectional view of the wave section in the area of the open cross-sectional profile,
• 4 a cross-sectional view of the wave segment in the area of the functional surface,
• 5 a perspective partial view of the shaft protection sleeve,
• 6 a perspective partial view of another version of the shaft protection sleeve,
• 7 a perspective partial view of an alternative design of the shaft protection sleeve,
• 8 a perspective partial view of another alternative design of the shaft protection sleeve,
• 9 a perspective partial view of another alternative design of the shaft protection sleeve,

1 Figure 1 shows a perspective top view of a shaft section. The arrangement 1 comprises a shaft 2 and a first embodiment of a sleeve 3. The sleeve 3 has a first region 4 with a functional surface 4a and a closed cross-sectional profile. On both sides of the first region or the functional surface 4a, the sleeve 3 has a second region 5 with an open cross-sectional profile, each with several slots 6, wherein the embodiment shown has five slots 6 on each side.

The first section 4 of the sleeve 3, or functional surface 4a, is separated from the two second sections 5 with open cross-sectional profiles by a transition 7 with respect to diameter. In this embodiment, the sleeve 3 is designed as a high-strength, wear-resistant ceramic sleeve with a lower coefficient of thermal expansion compared to the shaft 2. The shaft 2 is made of a steel material and is therefore more susceptible to corrosion and less wear-resistant than the sleeve 3, and has a higher coefficient of thermal expansion.

Every second area 5 with the open cross-sectional profile of the sleeve 3 has increased elasticity due to the slotting 6 and can accommodate thermally induced changes in length and/or thermally induced changes in diameter of the shaft 2 without loss of fit of the sleeve 3 on the shaft 2 and/or without thermally induced stresses arising.

In 2 is a cross-sectional view of the area in the 1 The wave section shown is depicted. It is evident that essentially in the area of the functional surface 4a or the first region 4, a A cavity 8 is formed between the sleeve 3 and the shaft 2. The slots 6 of the second area 5 extend at least to the cavity 8.

In the illustrated embodiment, the cavity 8 is formed by cutting out the sleeve 3. In an embodiment not shown, the cavity 8 can be formed by cutting out the shaft 2.

In 3 is a cut through sleeve 3 along the line in the 2 The line EE shown is depicted in the area of the second region 5. In this embodiment, five slots 6 are formed in the sleeve 3, creating five annular segments 11 that can accommodate a thermal differential expansion of the shaft 2 in the form of a bend. The transition 7 is also visible.

The 4 shows a section through sleeve 3 along the line in the 2 The line FF shown is in the area of the functional surface 4a, i.e., the first area 4.

5 Figure 1 shows a perspective partial view of the sleeve 3 in the version as a shaft protection sleeve 3. The five slots 6 of the open cross-sectional profile in the second area 5 have an axial longitudinal extent L, are aligned parallel to the sleeve axis 9 and are essentially perpendicular to the surface of the sleeve 3.

Each slot 6 has a width b that essentially corresponds to the end-face wall thickness d of the sleeve 3. The slots 6, in the form of recesses, each have the same length, the axial length or extent of which in this embodiment is a factor of more than 0.05 and less than 0.3 of the length of the sleeve 3.

The arrangement in 6 essentially corresponds to the representation in 3 , whereby in 4 The outlet of the slot 6 is rounded. In the illustrated embodiment, the rounding 10 is achieved by a bore in the second region 5, the bore having a larger diameter D than the width b of the slot 6. The rounded end of the slot 6 provides advantageous protection against high stresses in the sleeve 3 and effectively prevents component cracking. The rounding 10 is located near the transition 7, or near the first region 4, or the functional region 4a.

The version of the 7 differs from the version in 5 The slot 6 is oriented at an angle α. Each slot 6 is oriented at an angle to an imaginary line 12 parallel to the sleeve axis 9. For example, line 12 lies in the same plane as the sleeve axis 9, and simultaneously lies in the same plane as the surface of the sleeve 3. In the illustrated embodiment, the angle α is 45° in each case. This forms five circular segments 11, each with a rhomboid base. The circular segments 11 act as elastic elements that can accommodate the thermal expansion of the shaft 2 in the form of bending.

The 8 shows the in 7 The embodiment is shown in a top view, a view of the end face of the sleeve 3, and a partial perspective view of the sleeve 3. From the central view of the sleeve 3, i.e., the view of the end face, it is evident that the slots 6 in the second region 5 are inclined at an angle φ to the surface of the sleeve 3. With an inclined slot 6, the angle φ between a center line L _M of the slot 6 and a tangential line _LT to the surface is greater than 15° and less than 90° in a clockwise direction.

In 9 Figure 3 shows a variant embodiment of the sleeve 3, which has a multi-stage slot 6 in the second region 5. In the illustrated embodiment, the angle α between the slot 6 and a line 12 parallel to the sleeve axis 9 is essentially 45°. The gradation of the slot 6 is achieved by the angle β, where the angle β is essentially 90°. The angles α and β are arranged relative to each other such that the slot extends longitudinally parallel to the sleeve axis 9.

10 Figure 1 shows a variant embodiment of the sleeve 3 in which the slots 6 are each corrugated. The corrugated slot 6 is either sinusoidal or S-shaped and, by way of example, but not necessarily, has a length of one period. The amplitude A of the corrugated slot 6 is essentially twice the wall thickness d of the sleeve 3.

It goes without saying that the ones in the 7 to 10 The depicted slots 6 may have a rounding 10 at their outlet, as shown in the 6 It is also evident that the axial length or extent of the slot 6 can be a factor of more than 0.05 and less than 0.3 of the length of the sleeve 3 in all embodiments.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 23 34 673 A1 [0005]
• DE 10 2022 106 442 A1 [0006]
• DE 10 2015 221 255 A1 [0009]
• DE 10 2018 214 650 A1 [0010]

Claims (15)

Centrifugal pump arrangement with an arrangement (1) comprising a shaft (2) and a sleeve (3), wherein the sleeve (3) has a first region (4) with a functional surface (4a) and a closed cross-sectional profile, wherein a cavity (8) is formed in the region of the functional surface (4a) between the sleeve (3) and the shaft (2), characterized in that the sleeve (3) has at least on one side of the first region (4) a second region (5) with an open cross-sectional profile with at least one slot (6). centrifugal pump arrangement according to Claim 1 , characterized in that the at least one slot (6) has an axial longitudinal extent. centrifugal pump arrangement according to Claim 1 or 2 , characterized in that the slot (6) is aligned at an angle to a line (12) parallel to the sleeve axis (9). Centrifugal pump arrangement according to one of the Claims 1 until 3 , characterized in that the slot (6) is wavy. Centrifugal pump arrangement according to one of the Claims 1 until 4 , characterized in that the slot (6) is formed essentially perpendicular to the surface of the sleeve (3). Centrifugal pump arrangement according to one of the Claims 1 until 5 , characterized in that the slot (6) is inclined at an angle to the surface of the sleeve (3). Centrifugal pump arrangement according to one of the Claims 1 until 6 , characterized in that the second area (5) has a simply stepped slot (6). Centrifugal pump arrangement according to one of the Claims 1 until 7 , characterized in that the second area (5) has a multi-stage slotted design (6). Centrifugal pump arrangement according to one of the Claims 1 until 8 , characterized in that the slot (6) has a width (b) with a factor of more than 0.3 and less than 1.5 of the end-face wall thickness (d) of the sleeve (3). Centrifugal pump arrangement according to one of the Claims 1 until 9 , characterized in that the slot (6) has a length of more than a factor of 0.05 and less than 0.3 of the length of the sleeve (3). Centrifugal pump arrangement according to one of the Claims 1 until 10 , characterized in that the outlet of the slot (6) has a rounding (10). Centrifugal pump arrangement according to one of the Claims 1 until 11 , characterized in that the slots (6) extend over the resting ends at least to the cavity (8). Centrifugal pump arrangement according to one of the Claims 1 until 12 , characterized in that the cavity (8) is formed by piercing the sleeve (3). Centrifugal pump arrangement according to one of the Claims 1 until 13 , characterized in that the cavity (8) is formed by cutting out the shaft (2). Use of a centrifugal pump arrangement with an arrangement (1) at high operating temperatures to reduce thermally induced mechanical stresses within the sleeve-shaft pairing.