Axially mountable plug-in shaft

Abstract

The invention relates to a centrifugal pump (1) comprising a shaft assembly (2) having a first self-supported shaft part (3) on which an impeller wheel (4) is arranged, and a second bearing-mounted shaft part (5) driven by a motor (6). The shaft parts (3, 5) have an interlockingly plugged connection (7), which is arranged within a thermal separation element (8). At least one respective end (9, 10) of the two shaft parts (3, 5) has at least one groove section (11, 12) and the groove sections (11, 12) form a circumferential groove (13) in the plugged connection, in which a connecting securing ring (14) engages for the purpose of axial securing.

Description

[0001] Description

[0002] Axially mountable stub shaft

[0003] The invention relates to a centrifugal pump with a shaft arrangement comprising a first cantilevered shaft part on which an impeller is arranged and a second bearing-supported shaft part which is driven by a motor.

[0004] Centrifugal pumps are based on the principle of energy transfer to a fluid by changing the swirl as a result of a torque that is triggered by a uniformly rotating impeller on the fluid flowing through it.

[0005] The centrifugal pump is a working machine according to the direction of energy flow, a fluid machine according to the type of energy conversion and a hydraulic fluid machine according to the type of fluid.

[0006] Centrifugal pumps come in a wide variety of designs and constructions, each of which uses a variety of shaft arrangements and pump shafts. A shaft arrangement encompasses all the shaft components that together form a pump shaft.

[0007] The shaft or shaft assembly in centrifugal pumps transmits the drive torque to the impellers. The shaft assembly or shaft is the central component of a pump rotor in centrifugal pumps and connects the impellers, shaft covers, bearings, balancing discs or pistons (if applicable), and the coupling, as well as other pump components belonging to the rotor, such as expansion rings, balancing discs, inductors, and shaft nuts.

[0008] DE 10 2019 004 976 B3 discloses a centrifugal pump with a shaft assembly that is rotatably mounted within a pump housing and connected to a drive unit. A fan unit for cooling the pump has a fan impeller mounted on the shaft assembly.

[0009] In addition to energy transmission, the shaft arrangement also has the task of centering the rotating elements of the pump rotor with the bores of the pump housing in such a way that the aforementioned parts do not touch each other as much as possible during operation, taking shaft deflection into account.

[0010] Furthermore, the effects of corrosion on the shaft material caused by contact with the conveying fluid must be considered. This means that a corrosion-resistant material must be used. Furthermore, the shaft material should not permanently deform over time, even under fluctuating temperatures, which would affect smooth running and clearances.

[0011] Pumps with heat-decoupled lanterns are now known for special applications.

[0012] DE 10 2020 133 832 A1 describes a pump assembly with a lantern. The lantern is arranged between a pump housing and a motor housing. Surface-enlarging elements for heat dissipation are arranged on the lantern.

[0013] DE 10 2021 005 120 A1 discloses a pump assembly with a lantern. The lantern connects a pump housing and a motor housing. At least one heat-conducting barrier is arranged within the lantern. DE 10 2021 005 123 A1 describes a pump assembly with a lantern that connects a pump housing and a motor housing. The lantern has a pump-side connection part and a motor-side connection part. An annular element is suspended between the connection parts via brackets.

[0014] Such compact lanterns, with struts and recesses for thermal decoupling of the pump housing from the motor housing, are not open at the sides, as is usual with lanterns. This provides an integral protection against unintentional intervention, but the familiar and routine assembly of the shaft assembly is difficult to implement.

[0015] The object of the invention is to provide a centrifugal pump with a shaft assembly that ensures simple and reliable assembly. The shaft assembly should be able to transmit the drive torque to the pump impeller and withstand the effects of a corrosive medium. Furthermore, the shaft assembly should be characterized by a compact design. The design of the shaft assembly should facilitate the replacement of spare parts. The shaft assembly should be simple and cost-effective to implement.

[0016] This object is achieved according to the invention by a centrifugal pump with a shaft arrangement according to the features of claim 1. Preferred variants can be found in the independent main claims, the subclaims, the description and the drawings.

[0017] According to the invention, the shaft parts have a positive-locking plug-in connection which is arranged within a thermal separating element, wherein at least one end of each of the two shaft parts has at least one groove section and the groove sections in the plug-in connection form a circumferential groove into which a connecting retaining ring engages for axial fixing.

[0018] Ideally, the shaft assembly is constructed in two parts, with a cantilevered shaft section and a bearing-supported shaft section. Preferably, the cantilevered shaft section is connected to the bearing-supported shaft section via a positive, plug-in connection. The cantilevered shaft section is designed to accommodate an impeller, while the bearing-supported shaft section is driven by a motor.

[0019] The term "groove" refers to an elongated recess and is preferably used for securing elements, for example, using a retaining ring. The groove can have a rectangular or trapezoidal cross-section. A groove is called a continuous groove if it extends across the entire surface of a body. A closed-circumferential groove has no discernible beginning or end.

[0020] A groove can also extend over more than one component and is then divided into groove sections. Advantageously, each shaft part of the shaft arrangement has a groove section, with the groove sections combined to form a circumferential groove. In the shaft arrangement as a cylindrical component, the circumferential groove extends over the outer surface of the cylindrical body, into which a retaining ring can then engage to axially fix the shaft parts. This prevents the shaft parts from moving towards or away from each other in the axial direction. The unity of the shaft parts to form a shaft arrangement is achieved by arranging a retaining ring in the circumferential groove.

[0021] In a particularly preferred variant of the invention, the retaining ring is designed as a snap ring.

[0022] A retaining ring or grooved ring is a machine element used to axially secure bolts in bores or components, such as rolling bearings, on a shaft or axle. These rings are standardized parts. The rings used in mechanical engineering are standardized according to DIN 471 for shaft grooves and DIN 472 for bore grooves. A retaining ring requires a groove for its positioning. This groove is first cut into a shaft from the outside, turned into a bore from the inside, or milled. The snap ring is used for shaft mounting and can be bent from round wire. It has an angled locking eyelet at each ring joint, into which a tool can engage to position or expand the snap ring.

[0023] Ideally, the shaft components are centered relative to each other with a cylindrical shaft-hub connection. Centering of the shaft components is extremely important for the alignment of the shafts, for the gap between the impeller and the housing, and for the smooth running of the shaft assembly. Centering is preferably achieved by a precisely fitting cylinder into a hollow cylinder.

[0024] In one embodiment of the invention, the cantilevered shaft part may have the cylinder for engagement in the hollow cylinder, wherein the bearing-supported shaft part has the hollow cylinder.

[0025] In a favorable embodiment of the invention, the bearing-supported shaft part has a cylinder of the cylindrical shaft-hub connection, which engages in a centering manner in the hollow cylinder of the self-supporting shaft part.

[0026] Ideally, the positive connection, alone or additionally, is designed with a two-flat and a corresponding two-flat recess, with one end of the shaft parts having a two-flat and another end having the two-flat recess.

[0027] The dihedral preferably serves as a mechanical connection in the form of a plug-in coupling for connecting two components. For this purpose, two component surfaces of one component are configured to be plane-parallel and, with a negative, preferably a recess of a second component, which has plane-parallel surfaces, form a corresponding pair of active surfaces for transmitting forces and / or torques.

[0028] The positive connection, using a double flat and a double flat recess, creates a backlash-free connection that reliably transmits the motor torque. Furthermore, this type of connection allows axial mounting, which is particularly advantageous for use in centrifugal pumps with lanterns without mounting windows.

[0029] The double flat and the double flat recess are preferably formed at one shaft end of the shaft parts. Additionally, the double flat and the recess can correspond to a cylindrical shape of the positive connection. For this purpose, for example, the cylindrical shaft end can have one or more shoulders. The double flat and / or the double flat recess can extend over the shoulders. In the case of a double shaft shoulder, a T-shaped double flat surface is formed, which is particularly favorable for the formation of the positive connection and the transmission of torque.

[0030] The dihedral thus represents a male part of the connection, which engages with the female part of the connection, the counter surface in the form of the dihedral recess.

[0031] The dihedral and the dihedral recess form two surfaces directly adjacent to each other.

[0032] In an alternative variant of the invention, the positive connection can be designed, alone or additionally, with a flat and the corresponding recess. In this variant, the two shaft parts each have only one groove section, which, when joined together, form a circumferential groove.

[0033] In the form-fitting and plug-in connection, both the cylindrical parts and the two-flat parts of the shaft parts engage with each other to form the shaft arrangement.

[0034] In an alternative variant of the invention, the positive connection can also be achieved using other shapes, for example, using multi-flat or oval connection shapes. In a preferred variant of the invention, one end of the shaft parts has a cylindrical cavity. A cylindrical end of the other shaft part preferably engages in this cylindrical cavity. In addition, the cylindrical shaft-hub connection can be at least partially supplemented by a positive connection with a double flat and a corresponding double-flat recess.

[0035] Ideally, the dihedral of one shaft part has an elongated section that, together with a cylindrical cavity in the other shaft part, forms a channel for venting the positive, plug-in connection. This variant does not require an additional venting device or vent hole, as ventilation is already incorporated into the assembly of the shaft parts. Preferably, a shaft section of the cylindrical shaft-hub connection includes at least one recess, which, together with the hub, forms an air channel for venting the cavity during assembly.

[0036] In an alternative variant of the invention, one end of the shaft parts has a vent hole. Since the cylindrical shaft-hub connection is designed for a very precise fit, resistance can arise when joining the shaft parts. This resistance is caused by the air in the hollow cylinder, which cannot escape. This advantageous vent hole enables efficient and resistance-free joining of the shaft parts.

[0037] Preferably, the vent hole can also be designed as a transverse hole in a shaft part.

[0038] In a particularly advantageous variant of the invention, the thermal separating element is designed as a lantern.

[0039] Ideally, at least one thermal barrier is installed within the lantern. Such a thermal barrier is particularly advantageous for thermally decoupling a pump housing through which a hot fluid flows from the drive motor. This protects the motor and its components, ensuring the pump operates within the desired operating range.

[0040] Ideally, at least one thermal barrier is installed in all central axial sections. This achieves thermal decoupling of the pump housing from the motor housing, as heat cannot be conducted via a direct axial connection between the housings.

[0041] Additionally or alternatively, the lantern may have one or more recesses, which are shaped in such a way that neither engagement nor assembly into or to the shaft parts or shaft assembly is possible. These recesses may represent a form of thermal barrier.

[0042] In a favorable variant of the invention, the second, bearing-supported shaft part is longer than the first, cantilevered shaft part by a factor of more than 1.5, preferably more than 2.0, in particular more than 2.5. Thus, the cantilevered shaft part is supported by the bearing-supported shaft part.

[0043] Ideally, the length of the positive, plug-in connection of the shaft parts is more than 10%, preferably more than 15%, in particular more than 20%, of the length of the shaft arrangement.

[0044] The type and shape of the positive, plug-in connection of the shaft parts, in particular through long interlocking of the shaft parts, realizes a supporting function of the bearing-supported shaft part on the cantilevered shaft part.

[0045] Ideally, the shaft assembly is at least partially made of stainless steel. At least the self-supporting shaft section that comes into contact with the medium is made of a corrosion-resistant material, while the bearing-supported shaft section of the shaft assembly without media contact is made of a material that is advantageous for mechanical stress and / or a cost-effective material. Advantageously, the shafts can be made of different materials.

[0046] Thus, for example, the self-supporting shaft in contact with the pumped medium can be made corrosion-resistant, for example from a material with a high alloy content, while the bearing-supported shaft part without contact with the pumped medium is made from a material selected according to the type of mechanical stress or cost-effective.

[0047] According to the invention, the centrifugal pump with a shaft assembly comprising a first cantilevered shaft part on which an impeller is arranged and a second bearing-supported shaft part driven by a motor is assembled using a method in which the shaft parts are axially mounted with a positive connection within a thermal separator. For axial fixation of the shaft parts to form a shaft assembly, a retaining ring is inserted into a circumferential groove.

[0048] According to the invention, a centrifugal pump with a shaft arrangement for conveying corrosive and / or hot media by means of a conveying device in block construction is used.

[0049] Due to the special design of the shaft assembly, no radial access is required for assembly via a lantern window. Ideally, the shaft assembly design exhibits an extremely low tendency toward imbalance. The multi-part design of the shaft assembly allows for easy and cost-effective replacement of individual parts of the shaft assembly without the need for entire assemblies to be disposed of unusably. The design of the shaft assembly favors a lantern, which, without a lantern window and without a bearing support, enables a particularly compact design of the centrifugal pump assembly.

[0050] Further features and advantages of the invention will become apparent from the description of embodiments based on the drawings and from the drawings themselves.

[0051] Fig. 1 is an exploded view of a centrifugal pump with a shaft arrangement,

[0052] Fig. 2 a sectional view of the shaft arrangement,

[0053] Fig. 3 is a plan view of the shaft arrangement,

[0054] Fig. 4 is a perspective view of a shaft part,

[0055] Fig. 5 is another perspective view of a shaft part.

[0056] Fig. 1 shows an exploded view of a centrifugal pump 1 with a thermal separator 8 and a shaft assembly 2 according to the prior art with a conventional shaft-hub connection. The thermal separator 8, in the form of a lantern, connects a pump housing 22 and an electric motor 6. The centrifugal pump 1 shown in the exemplary embodiment is used to pump fluids that, depending on the application, may have high temperatures.

[0057] The fluid enters the pump housing 22 of the centrifugal pump 1 through a suction port 23. The impeller 4 is arranged within the pump housing 22. The impeller 4 transfers kinetic energy to the fluid, which leaves the centrifugal pump 1 via the discharge port 24. The impeller 4 is non-rotatably connected to the cantilevered shaft part 3 of the shaft assembly 2.

[0058] Fig. 2 shows a sectional view of the shaft arrangement 2 according to the invention. The self-supporting shaft part 3 has a positive, plug-in connection 7 with the bearing-supported shaft part 5. The self-supporting shaft part 3 is shaped such that an impeller 4 (not shown) can be arranged on the shaft part 3. The bearing-supported shaft part 5 is designed such that it can be driven by a motor 6 (not shown). The end 9 of the shaft part 3 has a cylindrical cavity 17, while the end 10 of the shaft part 5 has a partially cylindrical extension 18. The shaft parts 3, 5 are centered to one another by a cylindrical shaft-hub connection, wherein the positive connection 7 is implemented using the dihedral 15 (not shown) and the corresponding dihedral recess 16 (likewise not shown).

[0059] The end 9 of the shaft part 3 also has an external groove section 12, which, together with the groove section 11 at the end 10 of the shaft part 5, forms a circumferential groove 13 in the plugged connection. A connecting retaining ring 14 is arranged engagingly in the groove 13 for the axial fixation of the shaft parts 3 and 5. Due to this advantageous design, the shaft parts 3 and 5 can also be mounted in a lantern without radial engagement and assembly options.

[0060] Fig. 3 shows a top view of the shaft assembly 2, in which the cantilevered shaft part 3 has a positive, plug-in connection 7 with the bearing-supported shaft part 5. The positive, plug-in connection 7 is axially secured with a connecting retaining ring 14. The second, bearing-supported shaft part 5 is 2.5 times longer than the first cantilevered shaft part 3.

[0061] As a result, the shaft arrangement 2 tends to exhibit extremely low imbalance and enables a very compact design without a bearing support for the self-supporting shaft section 3. If the impeller seat is damaged, the entire motor is not rendered unusable, and the shaft sections 3 and 5 can be replaced separately. In this design variant, the self-supporting shaft section 3 is made of a material with the identifier 1.4404, and the bearing-supported shaft section 5 is made of a material with the identifier 1.0044.

[0062] Fig. 4 shows a perspective view of the end 10 of the shaft part 5. The shaft part 5 has an extension 18 which extends from the phase 19 partly cylindrical and partly with a dihedral 15. The extension 18 is designed in two stages, with the extension 18 initially having a part 20 with a larger diameter and a part 21 with a smaller diameter. The part 20 of the extension 18 is designed such that it completes the groove section 11 with the corresponding groove section 12 to form the circumferential groove 13. The part 21 of the extension 18 has a partial cylindrical contour to form the positive, plug-in connection 7, in which the part 21 is inserted into the cylindrical cavity 17 of the shaft part 3. Due to the two-stage shape of the extension 18, in the embodiment shown, a t-shaped dihedral 15 is formed with the elongated piece 25, with dihedral surfaces arranged planar to one another.The dihedral 15, together with the corresponding dihedral recesses 16 (not shown), also forms the part of the positive-locking, plug-in connection 7 that transmits torque from the shaft part 5 to the shaft part 3. In the plug-in version, the elongated piece 25 of the dihedral 15, together with the cylindrical cavity 17, forms a venting chamber from which the air in the cavity 17 can escape. Fig. 5 shows a perspective view of the end 9 of the shaft part 3. The end 9 has the groove section 12 arranged on the outside of the cylindrical surface and the internal dihedral recess 16, which merges into the cylindrical cavity 17.

Claims

Patent claims Axially mountable stub shaft 1. Centrifugal pump (1) with a shaft arrangement (2) which has a first cantilevered shaft part (3) on which an impeller (4) is arranged, and a second bearing-supported shaft part (5) which is driven by a motor (6), characterized in that the shaft parts (3, 5) have a positive-locking plug-in connection (7) which is arranged within a thermal separating element (8), wherein at least one end (9, 10) of each of the two shaft parts (3, 5) has at least one groove section (11, 12) and the groove sections (11, 12) in the plug-in connection form a circumferential groove (13) into which a connecting retaining ring (14) engages for axial fixing.

2. Centrifugal pump according to claim 1, characterized in that the retaining ring (14) is designed as a snap ring.

3. Centrifugal pump according to claim 1 or 2, characterized in that the shaft parts (3, 5) are centered to each other by a cylindrical shaft-hub connection.

4. Centrifugal pump according to one of claims 1 to 3, characterized in that the positive connection (7) is designed with a two-flat surface (15) and a corresponding two-flat recess (16), wherein one end (9, 10) of the Shaft parts (3, 5) have a dihedral (15) and the corresponding end (9, 10) of the other shaft part (3, 5) has the dihedral recess (16). Centrifugal pump according to one of claims 1 to 4, characterized in that one end (9, 10) of the shaft parts (3, 5) has a cylindrical cavity (17). Centrifugal pump according to one of claims 1 to 5, characterized in that the dihedral (15) has an elongated piece (18) which, together with a cylindrical cavity (17), forms a channel for venting the positive, plug-in connection (7). Centrifugal pump according to one of claims 1 to 6, characterized in that one end (9, 10) of the shaft parts (3, 5) has a vent hole. Centrifugal pump according to one of claims 1 to 7, characterized in that the thermal separating element (8) is designed as a lantern.Centrifugal pump according to one of claims 1 to 8, characterized in that the second bearing-supported shaft part (5) is longer than the first self-supporting shaft part (3) by a factor of more than 1.5, preferably more than 2, in particular more than 2.

5. Centrifugal pump according to one of claims 1 to 9, characterized in that the shaft arrangement (2) is formed at least partially from a stainless steel material. Method for assembling a centrifugal pump (1) according to one of claims 1 to 10 with a shaft arrangement (2) which has a first self-supporting shaft part (3) on which an impeller (4) is arranged, and a second bearing-supported shaft part (5) which is driven by a motor (6), characterized in that. characterized in that the shaft parts (3, 5) are mounted axially with a positive connection (7) within a thermal separating element (8). Use of a centrifugal pump (1) with a shaft arrangement (2) according to one of claims 1 to 10 for conveying corrosive media by means of a block-type conveying device.

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