US20210095685A1

US20210095685A1 - Pump shaft with fastening bolts

Info

Publication number: US20210095685A1
Application number: US17/019,060
Authority: US
Inventors: Johann Justl; Thomas Bock; Thomas OBENDORFER
Original assignee: Evoguard GmbH
Current assignee: Evoguard GmbH
Priority date: 2019-09-26
Filing date: 2020-09-11
Publication date: 2021-04-01
Also published as: DE202019105336U1

Abstract

A retaining device for an impeller of a centrifugal pump, including: a pump shaft with a recess formed substantially parallel to the axis of rotation of the pump shaft; a fastening bolt, which is insertable into the recess such that a first channel is defined between the inserted fastening bolt and the pump shaft and which is connected to the pump shaft on one end thereof and provides a retainer for fixing the impeller on the other end thereof; wherein the pump shaft includes at least one further channel extending from the circumferential surface of the pump shaft up to and into the recess and allowing the first channel to be emptied.

Description

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to German Patent Application No. 20 2019 105 336.4 filed on Sep. 26, 2019. The entire contents of the above-listed application are hereby incorporated by reference for all purposes.

TECHNICAL FIELD

The present invention relates to a retaining device for an impeller of a centrifugal pump.

BACKGROUND

Driving a centrifugal pump via a suitable, powerful motor is known in the prior art. The centrifugal pump typically has an impeller with blades or vanes, which drive the medium to be pumped. The drive work of the motor is converted into kinetic energy of the medium. In order to transmit the driving force of the motor to the centrifugal pump, the motor is provided with a motor shaft. This shaft often has a stub-like design. The centrifugal pump, in turn, has a pump shaft as the unit that transmits the driving force of the motor between the motor shaft and the pump impeller. The pump shaft is typically configured as a hollow shaft on the motor side. It is connected to the motor shaft on one end thereof and to the pump impeller on the other end thereof. The pump shaft is usually connected to the motor shaft via a press-fit or shrink-fit connection, so as to transmit the forces in question and ensure high concentricity.
In known pumps, the impeller is usually attached to the pump shaft from the front and secured against rotation through form-fit geometry. Axial fixing of the impeller takes place by screw fastening via a central nut, which is screwed onto a threaded stud provided on the end of the pump shaft. This threaded stud is usually formed directly on the pump shaft by means of turning and thus normally has a very short clamping length, which, in practice, may cause the pump nut and the impeller to disengage if vibrations occur. This usually results in destruction of the pump.
For pumps used in the food industry, it is indispensable that all points of separation formed in the product area between the individual components are sealed hygienically. This applies in particular to the points of separation between the pump impeller and the pump nut and between the pump impeller and the rotating part of the mechanical seal. In addition, especially for pumps with a mechanical seal capable of being cleaned with a liquid, a third seal may be placed between the mechanical seal and the pump shaft.
These seals create a cavity between the pump shaft and the impeller which is not ventilated. Such dead spaces may cause sterility or hygiene problems in the pumps used, e.g. when the latter are used in the food industry. Especially if a sealing element becomes leaky, there may be an ingress of leakage into this space, which cannot be removed by normal cleaning and cannot be detected from the outside.
Taking into account these problems, it is the object of the present invention to provide a pump shaft for a centrifugal pump, in the case of which the above-described sterility or hygiene problems are reduced or do not occur at all.

SUMMARY

Disclosed is a retaining device for an impeller of a centrifugal pump, comprising a pump shaft with an opening formed substantially parallel to the axis of rotation of the pump shaft; a fastening bolt, which is insertable into the opening and may be adapted to be screw-fastened on the end of the latter, so that a channel is defined between the inserted bolt and the pump shaft; wherein the pump shaft comprises on at least one end of the opening at least one channel extending from the circumferential surface of the pump shaft up to and into the opening and allowing the channel to be emptied.
The terms opening and recess are to be understood as synonyms when used herein.
The fastening bolt is advantageously at the end of the central bore and may be screw-fastened to the pump shaft, so that the at least one additional channel, which vents the central channel, ends into the pump lantern between the pump casing and the motor, thus allowing detection of a leakage and venting of the space between the pump impeller and the pump shaft.
Due to the depth of the bore, an increased length of the fastening bolt is obtained, which, in turn, substantially extends the clamping length in comparison with a threaded stud formed by turning and thus increases the safety against loosening of the impeller nut. The fastening bolt may advantageously be configured as a waisted stud bolt with rolled threads.
In some aspects, the retaining device the fastening bolt may be threaded and bracing may take place by screwing.
In other aspects, the retaining device, the fastening bolt may be insertable into and removable from the opening from at least one end of the pump shaft.
Additionally provided herein is a centrifugal pump for use in plants for producing foodstuff, cosmetics and pharmaceutical products, comprising: a pump casing; an impeller with impeller blades for feeding a medium in the pump casing; and a retaining device of the type described hereinbefore.
In the centrifugal pump the channel in the pump shaft may, in the retaining device, be longer than the thickness of the impeller and of the one or the plurality of mechanical seals, measured along the axis of rotation of the pump shaft.
In the centrifugal pump, the retaining device with the pump shaft may, in the area in which the pump casing overlaps the pump shaft, comprise one or a plurality of channels produced by boring and extending from the circumferential surface of the pump shaft up to the central bore, said channels allowing access to the channel in the area of the pump casing.
In the centrifugal pump, mechanical seals may be used for sealing the pump shaft against the pump casing.
The mechanical seal may seal the pump shaft against the pump casing in a suitable manner.
In the centrifugal pump, the transverse bores may allow communication between the channel and the area behind the mechanical seals. In this way, this area can be vented and emptied.
The mechanical seals may be flushable or rinsable, e.g. they may be capable of being cleaned by flushing the bearing, typically using some fluid.
In the centrifugal pump, the pump casing and/or the impeller may be replaceable.
In the centrifugal pump, the pump shaft may be connectable to a motor shaft. The pump shaft may be adapted to be braced onto the motor shaft by means of a clamping element.
Further provided is an apparatus in the field of foodstuff and drink and tobacco handling, such as a bottling plant or a tank storage, the apparatus comprising one or a plurality of the centrifugal pumps of the type described hereinbefore.

BRIEF DESCRIPTION OF THE FIGURES

In the following, embodiments of the present invention will be described making reference to the figures. The embodiments described are to be regarded as being merely illustrative in all respects and as being non-limiting, and various combinations of the features disclosed are comprised in the present invention.

FIG. 1A: a schematic view of a centrifugal pump according to an embodiment.

FIG. 1B: a schematic side view of the centrifugal pump according to FIG. 1A.

FIG. 2: a schematic side view of a detail of a known centrifugal pump.

FIG. 3: a schematic view of a detail of FIG. 1B concerning the pump shaft according to an embodiment.

FIG. 4 a schematic view of a pump with a retaining device according to an embodiment, the embodiment in question having two mechanical seals and the possibility of cleaning the interior of the mechanical seals by flushing them with a liquid.

DETAILED DESCRIPTION

FIGS. 1-4 show example configurations with relative positioning of the various components. If shown directly contacting each other, or directly coupled, then such elements may be referred to as directly contacting or directly coupled, respectively, at least in one example. Similarly, elements shown contiguous or adjacent to one another may be contiguous or adjacent to each other, respectively, at least in one example. As an example, components laying in face-sharing contact with each other may be referred to as in face-sharing contact. As another example, elements positioned apart from each other with only a space there-between and no other components may be referred to as such, in at least one example. As yet another example, elements shown above/below one another, at opposite sides to one another, or to the left/right of one another may be referred to as such, relative to one another. Further, as shown in the figures, a topmost element or point of element may be referred to as a “top” of the component and a bottommost element or point of the element may be referred to as a “bottom” of the component, in at least one example. As used herein, top/bottom, upper/lower, above/below, may be relative to a vertical axis of the figures and used to describe positioning of elements of the figures relative to one another. As such, elements shown above other elements are positioned vertically above the other elements, in one example. As yet another example, shapes of the elements depicted within the figures may be referred to as having those shapes (e.g., such as being circular, straight, planar, curved, rounded, chamfered, angled, or the like). Further, elements shown intersecting one another may be referred to as intersecting elements or intersecting one another, in at least one example. Further still, an element shown within another element or shown outside of another element may be referred as such, in one example. It will be appreciated that one or more components referred to as being “substantially similar and/or identical” differ from one another according to manufacturing tolerances (e.g., within 1-5% deviation).
FIG. 1A shows a schematic view of a centrifugal pump 100. The centrifugal pump 100 comprises a motor 101 with a motor housing 102. The motor may be mounted on or with a base 103. The motor of the centrifugal pump may drive a motor shaft 1. The motor shaft 1 may be connectable to a pump shaft 2. The pump shaft 2 is connected to an impeller 5. The pump blades of the impeller 5 are not shown in FIG. 1A. In FIG. 1A, the motor shaft 1 and the pump shaft 2 are connected to each other. For the connection, the pump shaft 2 is configured as a hollow shaft at one end thereof. In addition, the motor shaft is configured as a stub shaft. The pump shaft 2 is pushed over the stub shaft of the motor shaft 1. To this end, the stub shaft of the motor shaft 1 and the pump shaft 2 are configured such that the pump shaft 2 surrounds the stub shaft of the motor shaft 1. An overlap area is formed. Over at least part of the overlap area between the pump shaft 2 and the motor shaft 1, a clamping element 3 may be provided (see FIG. 3). The clamping element 3 and the pump shaft 2 typically form a unit. The clamping element encompasses the pump shaft 2 and thus the motor shaft 1. The clamping element 3 creates a very large non-slip connection surface between the motor shaft 1 and the pump shaft 2, thus providing a stable, high concentricity of the pump shaft 2.
FIG. 1B shows a side view of the centrifugal pump 100 of FIG. 1A. On the right hand side of this FIG. 1B, the motor 101 is shown, at the center of the figure the motor shaft 1 and on the left hand side of the figure the pump shaft 2. In the area of the pump shaft 2, in particular of the impeller 5, an area Z is highlighted. This area Z is shown enlarged in FIG. 3.
FIG. 2 shows a detail Z′ of a known centrifugal pump 200. The detail Z′ in a known centrifugal pump corresponds approximately to the location of detail Z of FIG. 1B. FIG. 2 shows a pump shaft 202 having a pump impeller 205 with blades 211 attached thereto. The pump shaft 202 would continue to the right and may then be connected to a motor shaft, which is not shown here. The detail Z′ also shows a pump casing 204. FIG. 2 shows seals 215. The seals 215.1, 215.3 seal the parts mounted on the pump shaft, viz. the impeller 205 and the impeller nut 206, against the product area 225, and the seal 215.2 seals the movable part of the mechanical seal against the pump shaft. The seal 215.2 is in particular required for pumps having a mechanical seal capable of being cleaned by flushing with a liquid. The area 225 close to the product in question may also be referred to as product side or end side or suction side. In a purely illustrative area 201, which is drawn by dashed lines without regard to actual size ratios, a dead space may be formed between the pump shaft 202, the pump impeller 205 and the impeller nut 206. This dead space is very difficult to access in the known centrifugal pump 200 and therefore very difficult or impossible to clean in case of ingress of leakage. In addition, leakage occurring in this area cannot be detected from the outside. Furthermore, in this dead space there is the risk that pressure may build up when the temperature changes, and this pressure may return leakages, back into the product and thus lead to recontamination of further product batches.
FIG. 3 shows the area Z of FIG. 1B in an enlarged representation. FIG. 3 with the area Z shown is comparable to FIG. 2 and the area Z′ shown there. FIG. 3 essentially shows a pump shaft 2. In addition, it shows the pump shaft 2 in relation to a pump casing/pump cover 4, in which the impeller 5 of the centrifugal pump 100 rotates. The impeller 5 may have a number of blades or delivery elements 5.1. The pump shaft 2 is connected to the motor shaft 1. The pump shaft 2 is configured as a hollow shaft. The hollow end, shown here in the drawing on the right and identified by reference numeral 2.1, accommodates the stub shaft of the motor shaft 2. The impeller 5 is driven by the pump shaft 2 connected to the motor shaft 1. The pump shaft 2 is braced onto the motor shaft 2 by means of the clamping element 3.
FIG. 1B already indicates and FIG. 3 shows in detail that the pump shaft 2 is hollow and has a bolt or rod 17 inside. This bolt may be a fastening bolt. The bolt 17 is oriented along the axis of rotation of the pump shaft 2 and cylinder-symmetric thereto. The bolt 17 comprises two ends, 17.1 and 17.2. One of the ends of the bolt, in the drawing the end 17.2, faces the motor 101, the other one, in the drawing the end 17.1, faces away from the motor 101. The end 17.2 of the bolt is held by a retainer 23 in the motor-side end of the pump shaft bore. The end 17.1 may protrude beyond the pump shaft 2 and receives, by means of a retainer 21, the impeller nut 7 thereon, thus fixing the pump impeller 5 on the pump shaft. In particular, the fastening bolt 17 may be configured as a threaded bolt and the retainers 21 and 23, respectively, may have threads for retaining the bolt 17 by means of the thread. The fastening bolt 17 is thus oriented along the pump shaft 2 so that the center axis of the fastening bolt 17 and of the pump shaft 2 coincide.
In FIG. 3, it is additionally shown that the fastening bolt 17 extends in a channel 18. The channel 18 is a venting channel. The venting channel 18 has a slightly larger diameter than the fastening bolt 17 and is otherwise formed essentially concentrically around the fastening bolt 17. Similar to FIG. 2, the area 201 is also indicated in this case, again in a purely illustrative manner and not to scale. In the area 201, internal sealing elements, such as the seals 15.1, 15.2 and 15.3, are indicated. In contrast to FIG. 2, the venting channel 18 in FIG. 3 now allows access to the area 201, i.e. to the space that was practically inaccessible in FIG. 2. Hence, the venting channel 18 creates between the pump shaft 2 and the fastening bolt 17 a gap, which makes the area 201 accessible. This gap, i.e. the venting channel 18, can be used to discharge leakage in the event of a partial failure of a sealing element. The leakage can here enter the venting channel 18 on the end side or via one or a plurality of additional channels. Such additional channels are identified by reference numerals 19.2 and 19.3 in FIG. 3. Furthermore, in the bottom of the pump shaft 2, another channel is shown, which is identified by reference numeral 19.1 and through which leakage can exit in the area of the lantern between the pump casing and the motor.
In other words, FIG. 3 shows a centrifugal pump 100 and a pump shaft 2 for this centrifugal pump 100 with a recess in the pump shaft 2 formed substantially parallel to the axis of rotation of the pump shaft 2. The pump shaft 2 has provided therein a fastening bolt 17. This fastening bolt 17 can be inserted into the recess, so that a channel 18 will be formed between the fastening bolt 17 and the pump shaft 2, when the fastening bolt has been inserted into the bore. This means that, at least in an area of the recess, the channel 18 is equal to a venting gap, when the fastening bolt 17 has been inserted into the bore. The fastening bolt 17 is braced with the pump shaft 2 at one end of the pump shaft making use of a respective retainer 23. At least one channel 19.1 is provided in the pump shaft 2 at at least one end of the recess, the channel starting on the circumferential surface of the pump shaft 2. This channel 19.1 extends up to and into the venting channel 18, so that the channel 18 can be emptied.
The long clamping length of the threaded connection between the pump shaft 2 and the impeller nut 7 via the fastening bolt 17 increases the safety against loosening of the impeller nut 7 and thus of the impeller 5 from the pump shaft 2. In addition, the leakage channels/venting channels 18 and 19.1, 19.2, 19.3 allow detection of a defect of the internal sealing elements 15.1, 15.2 and 15.3. By venting the interior in the area 201, a pressure build-up in this area is prevented and thus the risk of recontamination in the event of failure of a seal is minimized.
FIG. 4 shows a detail, comparable to detail Z in FIG. 3, of a pump provided with the retaining device described, but in a version with two mechanical seals 8, 9. Where identical elements are identified, FIG. 4 uses the same reference numerals as FIG. 3. The two mechanical seals 8 and 9 may be alike. Furthermore, there is the possibility of cleaning the inside of the mechanical seals by flushing them with a liquid. For this purpose, a flushing channel 403 is indicated in the figure. In FIG. 4 it can also be seen that the venting channel 18 penetrates the pump impeller 5 and both mechanical seals 8, 9 along the longitudinal axis and is then vented to the outside via the channel 19.1 and through a driver 401.

Claims

1. A retaining device for an impeller of a centrifugal pump, comprising:

a pump shaft with an opening formed substantially parallel to an axis of rotation of the pump shaft;

a fastening bolt insertable into the opening such that a channel is defined between the inserted fastening bolt and the opening of the pump shaft,

wherein the fastening bolt is connected to the pump shaft on one end thereof and provides a retainer for fixing the impeller on an other end thereof,

wherein the pump shaft comprises at least one further channel extending from a circumferential surface of the pump shaft up to and into a recess and allowing the channel defined between the inserted fastening bolt and the opening of the pump shaft to be emptied.

2. The retaining device according to claim 1, wherein the fastening bolt is a threaded bolt having a thread on at least one of its ends.

3. The retaining device according to claim 1, wherein the retainer is provided with a thread and bracing is accomplished by screwing.

4. The retaining device according to claim 1, wherein the fastening bolt is insertable into and removable from a bore from at least one end of the pump shaft.

5. The retaining device according to claim 1, wherein the opening formed substantially parallel to the axis of rotation of the pump shaft extends through a length of the pump shaft.

6. The retaining device according to claim 1, wherein the opening formed substantially parallel to the axis of rotation of the pump shaft does not extend through a length of the pump shaft.

7. A centrifugal pump for use in plants for producing foodstuff, cosmetics and pharmaceutical products, comprising:

a pump casing;

an impeller with impeller blades for feeding a medium in the pump casing; and

a retaining device comprising:

wherein the fastening bolt is connected to the pump shaft on one end thereof and provides a retainer for fixing the impeller on an other end thereof, and

8. The centrifugal pump according to claim 7, wherein, measured along the axis of rotation of the pump shaft, the channel in the pump shaft is longer than a thickness of the impeller and of an area which one or a plurality of mechanical seals on the pump shaft overlap.

9. The centrifugal pump according to claim 7, further comprising one or a plurality of mechanical seals for sealing the pump shaft against the pump casing.

10. The centrifugal pump according to claim 9, wherein an area between the plurality of mechanical seals is configured to be rinsed.

11. The centrifugal pump according to claim 7, wherein the pump shaft is provided with one or a plurality of channels in an area in which the pump casing overlaps the pump shaft, the channels extending from the circumferential surface of the pump shaft up to the opening, which is formed substantially parallel to the axis of rotation of the pump shaft, and allowing access to the channel defined between the inserted fastening bolt and the opening of the pump shaft.

12. The centrifugal pump according to claim 11, wherein the plurality of channels in the area in which the pump casing overlaps the pump shaft allow communication between the channel defined between the inserted fastening bolt and the opening of the pump shaft and an area behind the internal sealing elements.

13. The centrifugal pump according to claim 7, wherein the pump casing and/or the impeller are replaceable.

14. The centrifugal pump according claim 7, wherein the pump shaft is connectable to a motor shaft.

15. The centrifugal pump according to claim 7, wherein the pump shaft is adapted to be braced onto a motor shaft via a clamping element.