EP2746586A1

EP2746586A1 - A centrifugal pump with shaft locking device

Info

Publication number: EP2746586A1
Application number: EP12198370.4A
Authority: EP
Inventors: Hannu Makkonen; Janne Ripattila
Original assignee: Sulzer Pumpen AG
Current assignee: Sulzer Pumpen AG
Priority date: 2012-12-20
Filing date: 2012-12-20
Publication date: 2014-06-25

Abstract

The present invention relates to a centrifugal pump, especially to a close coupled centrifugal pump. The centrifugal pump (10) is provided with means (22, 24, 26) for preventing the rotation of the shaft (18) of the pump (10) when installing or dismantling the impeller (20) at the end of the shaft (18).

Description

Technical field

The present invention relates to a centrifugal pump. The present invention relates especially to a centrifugal pump - drive motor combination, the structure of which is simplified by arranging the impeller of the centrifugal pump to be supported by the bearings of the electric drive motor. Such a pump is generally called a Close Coupled centrifugal pump.

Background art

Close Coupled centrifugal pumps do not, as already mentioned above, have separate bearings for the shaft of the impeller, but the bearings of the electric motor carry all the loads subjected to the shaft, i.e. both radial and axial forces as well as the weight of the impeller and the shaft end hanging outside the housing or bearings of the electric motor. In close coupled centrifugal pumps the shaft of the electric motor may extend to such a length that the centrifugal impeller is fastened directly to the end of the shaft of the electric drive motor or the electric drive motor may be a standard one having a substantially short shaft extending out of the motor housing. In the latter case the shaft of the impeller or, in fact, of the centrifugal pump is arranged as an extension of the shaft of the electric motor with an ordinary connection, for instance a key-sleeve connection to the end of the shaft of the electric motor.
A problem relating to the close coupled centrifugal pumps relates to the installation or dismantling of the impeller. In other words, when the nut at the end of the impeller shaft should be tightened or loosened, the shaft of the pump and that of the electric motor tend to rotate. Such a rotation should be prevented, but normally the electric motors are not provided with any means for that purpose. For instance, the end of the motor opposite to the freely hanging shaft end is closed such that the end of the shaft is not even visible. Additionally, the fan cooling the electric motor is normally attached to the end of the shaft, whereby the fan should be dismantled to get access to the shaft. At the opposite end, the shaft is the only visible component.

Brief summary of the Invention

Thus an object of the present invention is to develop a new type of a centrifugal pump capable of solving the above discussed problem.
Another object of the invention is to develop such a novel fastening means or centrifugal pump casing or adapter for combining the centrifugal pump to the electric drive motor that includes means for preventing the shaft of the centrifugal pump and that of the motor from rotating when installing or dismantling the impeller of the centrifugal pump at the end of the shaft.
At least one of the objects of the present invention is fulfilled by a centrifugal pump having a shaft, an impeller on the shaft and a volute casing housing the impeller, the volute casing being attached by fastening means to an electric drive motor having a shaft, the shaft of the electric motor supporting the impeller of the centrifugal pump, where the fastening means and the shaft are provided with means for preventing the rotation of the shaft.
Other characterizing features of the centrifugal pump of the present invention become evident in the accompanying dependent claims.

Brief Description of Drawing

The centrifugal pump of the present invention is described more in detail below, with reference to the accompanying drawings, in which

Fig. 1 illustrates schematically a partial cross sectional view of a close coupled centrifugal pump in accordance with a first preferred embodiment of the present invention,
Fig. 2 illustrates schematically a partial cross sectional view of a close coupled centrifugal pump in accordance with a second preferred embodiment of the present invention,
Fig. 3 illustrates schematically a partial cross sectional view of a close coupled centrifugal pump in accordance with a third preferred embodiment of the present invention, and
Fig. 4 illustrates schematically a more detailed partial cross sectional view of a close coupled centrifugal pump of Fig. 3.

Detailed Description of Drawings

Figure 1 is a general partial cross sectional illustration of a close coupled centrifugal pump 10 in accordance with a first preferred embodiment of the present invention. The close coupled centrifugal pump 10 shown in Fig. 1 comprises an electric drive motor 12 with an attachment flange 14 attached or arranged or integrated to its housing and a centrifugal pump volute casing (not shown) attached to the flange 14 of the drive motor 12 by fastening means 16. The fastening means may be formed of the pump casing or be an adapter part separately attached thereto. The fastening means 16 surrounds a shaft 18 of the electric motor 12, which extends to such a length that the shaft 18 of the electric motor 12 acts as the shaft of the centrifugal pump, too. The impeller 20 of the centrifugal pump is attached to the end of the shaft 18. Naturally, the impeller 20 is located within the volute casing (not shown in the drawings) attached to the fastening means 16.
The problem leading to the present invention, i.e. for preventing the shaft 18 of both the electric motor 12 and the centrifugal pump from rotating when installing or dismantling the impeller, or, in fact, when tightening or loosening the nut at the end of the shaft 18, is solved by arranging means for preventing the rotation of the shaft 18 in connection with both the shaft 18 and the fastening means 16. The rotation preventing means comprises a hole 22 in the fastening means 16, a rotation stopper 24 in connection with the shaft 18, and a locking pin 26 insertable in the hole 22 and cooperating or communicating, when desired, with the rotation stopper 24.
The hole 22 in the fastening means 16 is preferably, but not necessarily, substantially radial. However, it is also possible to arrange the hole 22 to be somewhat inclined, as long as the hole 22 in the fastening means 16 is aligned with the rotation stopper 24 such that in at least one rotational position of the shaft 18 the locking pin 26 may be pushed to cooperate with the rotation stopper 24. The inclination of the hole 22 may be arranged in both radial and axial direction, if desired. The rotation stopper 24 in the shaft 18 is preferably a blind hole, though also a through-bore may be applied. The diameter/s of the holes correspond/s to the diameter/s of the locking pin such that there is a sliding clearance between the holes and the pin 26. It is also worthwhile understanding that a rotation stopper 24 in connection with the shaft 18 may be replaced with a series of rotation stoppers arranged on the circumference of the shaft 18. The rotation stopper/s 24 may not only be formed of hole/s but it/they may as well be one or more axially extending grooves on the circumference of the shaft, or one or more axially extending radial protrusions, here called as tooth/teeth, arranged on the circumference of the shaft 18.
As to the locking pin 26, a further advantageous, but not necessary, feature of the locking pin 26 is that it is provided with means for locking the pin 26 in its axial direction into two positions, one for locking the shaft immobile, and another for locking the pin in its non-operative position i.e. the radially inner end of the pin 26 at a distance from the rotation stopper/s 24 in or on the shaft 18. Such means may, for instance, be a spring loaded ball or pin arranged in connection with the hole 22 in the fastening means 16, and two circumferential grooves on the pin surface. The locking means functions such that the spring pushes the ball or pin radially against the locking pin 26, and when the ball or pin hits the groove, the locking pin requires some force to move out of this locked position. A first groove is positioned such that when the ball is positioned in the groove, the locking pin 26 extends into communication with the rotation stopper 24 preventing the shaft 18 from rotating. The second groove is positioned closer to the end of the locking pin 26 used for locking the rotation of the shaft 18 such that when the ball is in the second groove the locking pin 26 does not any more extend into communication with the rotation stopper 24, but allows the shaft to rotate freely.
Figure 2 illustrates a partial cross sectional view of a close coupled centrifugal pump in accordance with a second preferred embodiment of the present invention. In Figure 2 the reference numerals cite to corresponding members or elements shown already in Figure 1. Here, the only difference to the first preferred embodiment of Figure 1 is that now the shaft 28 of the centrifugal pump is arranged to be a separate extension arranged to the end of the shaft 18 of the electric motor 12. The end of the shaft 28 opposite to the impeller 20, i.e. the end facing the electric motor 12, is formed of a sleeve 28' used for housing the end of the shaft 18 of the electric motor by ordinary ways of fastening, for instance by means of a key or shrink fitting (not shown). See Figure 4 for more detailed illustration. In other words, now the rotation stopper/s 24 similar to those discussed in connection with Figure 1 is/are arranged in connection with the sleeve 28' of the shaft 28 of the centrifugal pump.
Figure 3 illustrates a partial cross sectional view of a close coupled centrifugal pump in accordance with a third preferred embodiment of the present invention. In Figure 3 the reference numerals cite to corresponding members or elements shown already in Figure 2. Here, the only difference to the second preferred embodiment of Figure 2 is that the fastening means 16 is divided into two parts, namely the pump casing 30, housing for instance the sealing of the pump, and an adapter 32. Thus, the volute casing (not shown) is attached to the pump casing 30, and the pump casing via the adapter 32 to the flange 14 of the electric drive motor 12. Now, in this embodiment of the present invention the hole 22 for the pin 26 in the fastening means is arranged in the adapter 32. Also in this case the hole 22 is preferably radial, but it may be inclined, too, as long as it is aligned with the rotation stopper 24, whereby the direction of the hole may be called substantially radial. The ultimate option for the inclination of the hole 22 would be to arrange the corresponding rotation stopper 24 in connection with the sleeve 28' be such a hole that passes the interior cavity for the shaft 18 inside the sleeve 28' entirely (when looking from the axial direction). In other words, the hole passes the shaft 18 of the drive motor such that when the locking pin 26 is pushed into the hole 24 it is positioned to the side of the shaft 18 and not towards the shaft 18 as shown in the Figures.
In the manner already discussed above the rotation stopper 24 in connection with the sleeve 28' may not only be a single hole 24, but may be replaced with a series of corresponding holes or with one or more axially extending grooves or one or more axially extending members protruding substantially radially from the surface of the sleeve, here called as teeth.
Figure 4 illustrates a more detailed cross sectional view of the close coupled centrifugal pump 10 of Figure 3. In Figure 4 the reference numerals cite to corresponding members or elements shown already in earlier Figures 1. It shows, for instance, the sleeve 28' arranged by means of shrink fitting on the shaft 18 of the electric motor 12.
It has to be understood that, naturally, the fastening means construction of Figures 3 and 4 is applicable in connection with the pump in accordance with the embodiment discussed in Figure 1, i.e. the "split-fastening means" structure may be used with a unitary shaft construction, too.
The above described structure is very advantageous in view of the manufacture of the shaft and the fastening means/adapter. Naturally, another option would be to arrange the shaft 28 of the centrifugal pump or the shaft sleeve 28' to have, for instance, a square or hexagonal cross section or at least two flat opposite surfaces for a certain part of its length, and use a flat or adjustable spanner provided in an opening in the fastening means for the locking of the shaft 28 or the shaft sleeve 28'. However, the manufacture of a non-round cross section is much more complicated and, thus, expensive than drilling two holes. Also, as a tool for locking the rotation of the shaft a locking pin is much simpler than a flat spanner or an adjustable spanner.
As can be seen from the above description a novel centrifugal pump construction has been developed. While the invention has been herein described by way of examples in connection with what are at present considered to be the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various combinations and/or modifications of its features and other applications within the scope of the invention as defined in the appended claims.

Claims

A centrifugal pump having a shaft (18, 28), an impeller (20) on the shaft (18, 28) and a volute casing housing the impeller (20), the volute casing being attached by fastening means (16) to an electric drive motor (12) having a shaft (18), the shaft (18) of the electric motor (12) supporting the impeller (20) of the centrifugal pump (10), characterized in that the fastening means (16) and the shaft (18, 28) are provided with means for preventing the rotation of the shaft (18, 28).
The centrifugal pump as recited in claim 1, characterized in that the shaft (28) of the centrifugal pump (10) comprises a sleeve (28') at its end opposite to the impeller (20) for housing an end of the shaft (18) of the electric drive motor (12).
The centrifugal pump as recited in claim 1 or 2, characterized in that the rotation preventing means is a hole (22) in the fastening means (16), a locking pin (26) and a rotation stopper (24) in connection with the shaft (18, 28) or the sleeve (28').
The centrifugal pump as recited in claim 3, characterized in that the fastening means (16) comprises a pump casing or a pump casing (30) and an adapter (32) and that the hole (22) is arranged in pump casing or in the adapter (32).
The centrifugal pump as recited in claim 3, characterized in that the rotation stopper (24) is at least one hole, at least one axial groove or at least one axially extending radial projection or tooth.
The centrifugal pump as recited in claim 3, characterized in that the hole (22) in the fastening means (16, 32) is substantially radial.
The centrifugal pump as recited in claim 3, characterized in that the hole (22) in the fastening means (16, 32) is aligned with the rotation stopper (24) in connection with the shaft (18, 28) or sleeve (28').
The centrifugal pump as recited in claim 3, characterized in that the hole (22) in the fastening means (16, 32) is inclined.
The centrifugal pump as recited in claim 1 or 2, characterized in that the shaft (18, 28) or the shaft sleeve (28') is provided with a square or hexagonal cross section or at least two flat opposite surfaces for a certain part of its length, and that the fastening means (16) is provided with an opening for a flat or adjustable spanner for locking of the shaft (18, 28) or the shaft sleeve (28').
An adapter used for fastening a centrifugal pump (10) to an electric drive motor (12), characterized in that the adapter (32) is provided with a hole (22) for a pin (26) used for stopping the rotation of a shaft (18, 28) of the centrifugal pump (10) or an opening for a flat or adjustable spanner.
A shaft for a centrifugal pump, characterized in that it is provided with a rotation stopper (24).
The shaft as recited in claim 11, characterized in that it comprises a sleeve (28') for housing an end of a shaft of an electric drive motor (12) and that the sleeve (28') is provided with a rotation stopper (24).
The shaft as recited in claim 11 or 12, characterized in that the rotation stopper (24) is at least one hole, at least one axially extending groove or at least one axially extending radial projection arranged in or on the circumference of the shaft (18, 28) or the shaft sleeve (28').
The shaft as recited in claim 11 or 12, characterized in that the rotation stopper (24) comprises a square or hexagonal cross section or at least two flat opposite surfaces for a certain part of the length of the shaft (18, 28) or the shaft sleeve (28').