Patent Application
20200200189
This application claims the benefit of priority under 35 U.S.C. § 119 of European Application 18 21 4652.2, filed Dec. 20, 2018, the entire contents of which are incorporated herein by reference.
The present disclosure is directed to a pump assembly, in particular to a multi-stage centrifugal pump assembly.
The shape and size of a pump assembly is designed to meet certain technical requirements and specifications. In particular, multi-stage centrifugal pumps like the pumps of the Grundfos CR series come in a wide range of sizes to cover a power range of 0.1 to 100 kW. The more pumping power is needed, the larger the pump is typically designed.
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 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 flow the pump is supposed to be able to deliver, the radial extension of the impellers and the pump housing may be larger or smaller.
As one type of electric motor can be used for a certain range of pumps, different pumps within a certain performance range can be driven with the same type of motor. Vice versa, the same pump may be driven by a range of motors that come in different sizes. In order to adapt differently shaped pump housings to the same motor or the same pump housing to different sizes of motors, a motor stool typically serves as a mounting adapter between the motor and the pump. Thereby, standard electric motors can be used, which need not to be specifically designed to drive pumps and may be used in other fields.
It is known from EP 3 181 908 A1 to use four straps circumferentially distributed around the pump housing and extending axially alongside the pump housing for clamping the motor stool to the pump base.
In view of such known pumps, it is an object of the present disclosure to provide a pump assembly, which can be assembled more easily and is safer against unwanted disassembling.
In contrast to such known pumps, embodiments of the present disclosure provide a pump assembly, which can be mounted more easily and is safer against unwanted demounting.
In accordance with a first aspect of the present disclosure, a pump assembly is provided comprising
Thus, the tie rods cannot be unmounted as long as the motor housing is coupled to the motor stool. This prevents unwanted demounting of the tie rods as long as the motor is still coupled to the rotor shaft. Furthermore, the assembling process is easier compared to previously known pumps. As the fixation protrusions are placed within the motor stool with a certain distance to the radial periphery of the motor stool, the motor stool can be easily placed at the pump housing before the tie rods are fixed to the motor stool by way of the fasteners extending at least partially through the fixation protrusions. The fixation protrusions may be axial inner bores in the motor stool, i.e. they may be closed towards the radial periphery of the motor stool. Alternatively, one or more of the fixation protrusions may be recesses in the motor stool that extend radially inwardly, i.e. they may be open towards the radial periphery of the motor stool. However, irrespective of whether the fixation protrusions are open or closed towards the radial periphery of the motor stool, the fastener may comprise engagement means, e.g. a bolt head or a nut, for engaging a tool like a spanner or a hex, wherein the engagement means are laterally enclosed by the motor stool and only accessible axially from the side where the motor housing is to be coupled to the motor stool, i.e. when the motor housing is actually decoupled from the motor coupling portion of the motor stool. Preferably, a motor stool end portion of the tie rods is pulled by the fastener towards the motor coupling portion of the motor stool and away from the pump coupling portion of the motor stool. Thereby, the pump coupling portion of the motor stool is pushed towards the pump housing by a tension force conveyed by the tie rods. Accordingly, a pump base end portion of the tie rods pulls the pump base towards the pump housing, 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 tie rods.
Optionally, each of the tie rods may comprise a motor stool connection part at a motor stool end portion of the tie rod and a pump base connection part at a pump base end portion of the tie rod. Preferably, each of the tie rods may comprise a longitudinal panel, wherein said panel has a radially outer face and a radially inner face, wherein the motor stool connection part and/or the pump base connection part extend inwardly from the radially inner face of the panel towards the rotor axis. The panel may thus outwardly shield the motor stool connection part and/or the pump base connection part, so that they are not visible and/or accessible when the pump is fully assembled. At least a part of the radially outer face of the panel may be flush with the outer periphery of at least a part of the motor stool and/or the pump housing. Such part of the motor stool and/or the pump housing may comprise a longitudinal groove to accommodate at least a part of the panel essentially filling the longitudinal groove. This is particularly useful for pumps to be used in clean or sterile environments like the food industry, because flush and smooth surfaces are easier to keep clean and sterile.
Optionally, the motor stool may be clamped to the pump base by exactly two tie rods extending alongside the pump housing, wherein the fixation protrusions of the motor stool are located at diametrically opposite radial sides of the motor stool. The fixation of the tie rods to the motor stool by way of a fastener at least partially extending through one of the fixation protrusions allows for more tensile stress per tie rod compared to known four-strap fixation systems. Therefore, only two tie rods may be sufficient to securely hold the motor stool, the pump housing and the pump base together. This saves time for assembling the pump.
Optionally, each of the tie rods and/or the fixation protrusions may extend essentially parallel to the rotor axis. This is beneficial, because the main component of the tension force is essentially parallel to the rotor axis. However, the motor coupling portion of the motor stool may have a larger radial extension than the pump coupling portion of the motor stool, so that the motor stool may effectively widen towards the motor. It is thus possible that the tie rods and/or the fixation protrusions may not extend exactly parallel to the rotor axis.
Optionally, the motor stool may comprise at least two radially outwardly open motor stool recesses, wherein the protrusion end facing towards the motor housing is a first protrusion end, wherein each fixation protrusion comprises a second protrusion end facing towards the pump base and ending in one of the motor stool recesses, wherein each of the motor stool recesses accommodates a motor stool connection part of one of the tie rods. The motor stool recess may radially outwardly merge into a longitudinal groove at the motor stool for accommodating the motor stool end of the panel of the tie rod.
Optionally, the pump base may comprise at least two radially outwardly open pump base recesses, wherein each of the pump base recesses accommodate a pump base connection part of one of the tie rods. It is advantageous that the pump base connection part, in contrast to the motor stool connection part, is not actively fixed to the pump base by way of a fastener, but passively hooked into the pump base recess of the pump base for a secure positive form locking. Thus, each pump base recess may comprise an anchor face for positive form locking with a hook face of a pump base connection part of the tie rods. Preferably, the anchor face of the pump base recess may have an angular orientation with an angle β in the range of 0° to 60°, most preferably 0° to 15°, with respect to a plane perpendicular to the rotor axis, wherein the surface normal of the anchor face has a vector component pointing radially inward towards the rotor axis and/or downwards. Likewise, the hook face of the pump base connection part may have a corresponding angular orientation with the angle β in the range of 0° to 60°, most preferably 0° to 15°, with respect to a plane perpendicular to the rotor axis, wherein the surface normal of the hook face has a vector component pointing radially outward away from the rotor axis and/or upward. The contact between the anchor face and the hook face provides for a secure positive form locking of the pump base end portion of each tie rod.
Optionally, in order to make sure that the pump base connection part cannot slip off the pump base recess, at least one of the pump base recesses may comprise a securing face for abutting against the radial outer face of the panel of the tie rod, wherein the surface normal of the securing face has a vector component facing radially inward toward the rotor axis. Preferably, the securing face is located axially further away from the pump housing than the anchor face, wherein the pump base laterally widens in the direction away from the pump housing. Preferably, the securing face is located radially more outward than the outer periphery of the pump housing. Thereby, the panel of the tie rods can be designed straight in longitudinal direction.
In some cases, it may be advantageous for the anchor face and the hook face to have an angular orientation with a zero or negative angle β in the range of 0° to −30°, with respect to a plane perpendicular to the rotor axis, with the surface normal of the anchor face having a vector component pointing radially outward and the surface normal of the hook face having a vector component pointing radially inward. In such a case, the securing face may prevent the pump base connection part from slipping off the pump base recess.
Optionally, a panel of each tie rod may lie at least partially against a radially outer face of the pump housing. Thereby, a thermal contact may provide for an enhanced heat dissipation of the pump housing via the panels of the tie rods. Optionally, in order to enhance the thermal transfer between the pump housing and the panel, the tie rod may comprise a thermally conducting pad at the radially inner face of the panel. The pad may thus be placed between the panel and the pump housing transferring heat from the pump housing to the panel which has a relatively large radially outer face to radiate heat off and to be cooled by ambient air.
Optionally, the circumferential extension of the panels of all tie rods in cumulation may cover a fraction in the range of 1/18 to ¼ or more, preferably about ⅕ or about ⅙, of the circumference of the pump housing. Thereby, the tensile stress on the tie rods can be efficiently distributed over the width of the panels in circumferential direction. The circumferential extension of the panels may be constant or vary over their length. In case it varies over the length, the maximum of the circumferential extension of the panels of all tie rods in cumulation may cover a fraction in the range of 1/18 to ¼ or more, preferably about ⅕ or about ⅙, of the circumference of the pump housing.
Optionally, at least one of the fasteners may comprise an engagement means, e.g. a bolt head or a nut, for engaging a tool, e.g. a spanner or a hex, wherein the engagement means is laterally enclosed by the motor stool.
Optionally, the protrusion end in the motor coupling portion may be laterally enclosed by the motor stool and may form a laterally shielded inner seat for engagement means of the fastener within the motor coupling portion of the motor stool.
Optionally, at least one face of a panel of each tie rod may be arc-shaped in a cross-sectional plane perpendicular to the rotor axis, wherein the curvature of the arc-shaped face corresponds to a curvature of a radial outer face of the pump housing. This is not only beneficial to achieve a flush transition between the panel and the motor stool for an appealing aesthetic design and easier cleaning, but also increases the stiffness of the tie rods without adding weight and material to it.
Optionally, a panel of each tie rod may be stiff against bending perpendicular to the rotor axis, so that the motor stool end of the tie rod deflects by less than 5% of the tie rod length when a nominal test weight of 1 kg is applied vertically downward to the motor stool end of the tie rod while the tie rod is fixed horizontally at the base end of the tie rod. This is beneficial for coping with the tensile stress, in particular when only two tie rods are used to clamp the motor stool to the pump base.
Optionally, each of the fasteners may comprise a bolt, wherein a motor stool connection part of each tie rod comprises a thread for receiving the bolt. The bolt may comprise an outer thread to be inserted through the fixation protrusions of the motor stool and to be screwed into an inner thread of the motor stool connection part of the tie rod placed in the motor stool recess. Alternatively, the bolt may extend from the motor stool connection part placed in the motor stool recess through the fixation protrusions of the motor stool towards the motor housing to be fixed by a nut at the motor coupling portion of the motor stool.
Optionally, each of the protrusion ends facing the motor housing may comprise a counterbore, wherein each of the bolt heads is formed as a socket head and at least partially sunk into one of the counterbores. It is advantageous if the bolt heads to not axially protrude out of the motor coupling portion of the motor stool, because a variety of motor housings may thereby be mounted on the motor stool.
Optionally, each of the fasteners may comprise a nut with an inner thread portion, wherein a motor stool connection part of each tie rod comprises a bolt portion with an outer thread, the bolt portion extending through the fixation protrusion for receiving the inner thread portion of the nut located at the protrusion end facing towards the motor housing. Optionally, each of the fixation protrusions may comprise a counterbore, wherein each nut is at least partially sunk into one of the counterbores.
Optionally, a motor stool connection part of each tie rod is movable parallel to the rotor axis within a range inside a motor stool recesses, wherein an upper limit of the range is defined by a positive form locking between a hook face of a pump base connection part of the tie rod and an anchor face of a radially outwardly open pump base recess in the pump base.
Optionally, the pump base recess may be downwardly open so that a lower limit of the range is defined by the ground on which the pump assembly is standing.
Optionally, the pump assembly is a multi-stage centrifugal pump assembly.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.
In the drawings:
Referring to the drawings,
Each of the pump assemblies 1 comprises a pump base 3 (in the shown vertical pump setup at the bottom of the pump assembly 1), a pump housing 5, a motor stool 7 and a motor housing 9 (in the shown vertical pump setup at the top of the pump assembly 1) enclosing a motor. The motor drives an inner rotor shaft (not shown) extending along the vertical rotor axis R into the pump housing 5. The pump housing 5 rests on the pump base 3 and encloses a stack of two impeller stages 10 arranged between the motor stool 7 and the pump base 3. The pump base 5 serves as a stand for the pump assembly 1 and provides lugs or bores 11 for fixing the pump assembly 1 to the ground it stands on. The motor housing 9 is mounted on the motor stool 7 that serves as a mounting adapter between the pump housing 5 and the motor housing 9. The motor housing 9 is fixed to the motor stool 7 by accessible bolts 8. The motor stool 7 thus comprise a motor coupling portion 13 at a first (upper) axial end to attach the motor housing 9 and a pump coupling portion 15 at a second (lower) axial end to attach the pump housing 5.
The example shown
In all three examples shown in
At an upper motor stool end portion 25 of the tie rod 17, the tie rod 17 comprises a motor stool connection part 27 extending radially inward from the radially inner face 23. The motor stool connection part 27 may be made of steel and welded to the radially inner face 23 of the steel panel 19. Similarly, and better visible in
In this first embodiment, the motor stool 7 comprises two fixation protrusions 39 in form of inner bores each having a protrusion end 41 at the motor coupling portion 13. It is important to note that the protrusions 39 have a lateral distance to the outer periphery of the motor coupling portion 13 of the motor stool 7 so that the motor housing 9, when coupled to the motor stool 7, blocks the axial access to the upper protrusion end 41. The protrusion end 41 is thus inaccessible when the motor housing 9 is coupled to the motor stool 7. The protrusion end 41 is shielded against lateral access by the motor stool 7 itself.
As can be seen better in
The pump base connection part 31 at the lower pump base end portion 29 of the tie rod 17 projects radially inward into a radially outwardly open pump base recess 49 of the pump base 3. In order to provide for a secure positive form locking, each pump base recess 49 comprise an anchor face 51 for positive form locking with a hook face 53 of the pump base connection part 31. The anchor face 51 of the pump base recess 49 is inclined by an angle β in the range of 0° to 15° with respect to the horizontal xy-plane extending perpendicular to the rotor axis R. The surface normal N of the anchor face 51 has a vector component pointing radially inward towards the rotor axis R. Likewise, the hook face 53 of the pump base connection part 31 be correspondingly inclined by the angle β in the range of 0° to 15° with respect to the horizontal xy-plane extending perpendicular to the rotor axis R. The surface normal M of the hook face 53 has a vector component pointing radially outward away from the rotor axis R. The surface normal N and the surface normal M are essentially parallel with opposite vector directions. The contact between the anchor face 51 and the hook face 53 provides for a secure positive form locking of the pump base end portion 29 of each tie rod 17.
Each pump base recess 49 comprises a securing face 55 facing radially inward toward the rotor axis R for abutting against the radial outer face 21 of the panel 19 of the tie rod 17. The securing face 55 is located axially further away from the pump housing 5 than the anchor face 51. Furthermore, the securing face 55 is located radially more outward than the outer periphery of the pump housing 5. The pump base recess 49 is axially open to the bottom so that the pump base end portion 29 of the tie rod 17 can be placed into the pump base recess 49 when being inclined as shown in
A second embodiment is shown in
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.
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.
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.
While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.
| Number | Date | Country | Kind |
|---|---|---|---|
| 18214652.2 | Dec 2018 | EP | regional |
