PUMP SHAFT WITH FASTENING BOLTS
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.
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 FIELDThe present invention relates to a retaining device for an impeller of a centrifugal pump.
BACKGROUNDDriving 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.
SUMMARYDisclosed 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.
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.
In
In other words,
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.
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: 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, and
- 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.
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.
Type: Application
Filed: Sep 11, 2020
Publication Date: Apr 1, 2021
Inventors: Johann JUSTL (Sinzing), Thomas BOCK (Wackersdorf), Thomas OBENDORFER (Neunburg vorm Wald)
Application Number: 17/019,060