Title of Invention	A DEVICE ABSORBING THE AXIAL THURST OF A MULTISTAGE CENTRIFUNGAL PUMP.
Abstract	This invention relates to a device for absorbing the axial thrust of a multistage centrifugal pump which possesses an axial gap (8), radial gaps (6, 7), an axial bearing (9) absorbing the remaining residual thrust. The axial bearing (9) is being assigned a cardanic ring (10) serving for the compensation of errors of alignment. The relieving device is designed in such as way that, in all the operating states, a residual thrust occurs which acts in the direction of the suction side of the centrifugal pump, and in that the cardanic ring (10) is dimensioned in such a way that it is deformed elastically by the residual thrust. The spring constant of the cardanic ring (10) possesses a characteristic such that, starting from a maximum gap width (s) in the state of rest of the centrifugal pump, the axial gap (s) (8) close (s) under operating conditions to a minimum width at which contact between the faces delimiting the axial gap (s) (8) is still avoided.

Title of Invention

A DEVICE ABSORBING THE AXIAL THURST OF A MULTISTAGE CENTRIFUNGAL PUMP.

Abstract

This invention relates to a device for absorbing the axial thrust of a multistage centrifugal pump which possesses an axial gap (8), radial gaps (6, 7), an axial bearing (9) absorbing the remaining residual thrust. The axial bearing (9) is being assigned a cardanic ring (10) serving for the compensation of errors of alignment. The relieving device is designed in such as way that, in all the operating states, a residual thrust occurs which acts in the direction of the suction side of the centrifugal pump, and in that the cardanic ring (10) is dimensioned in such a way that it is deformed elastically by the residual thrust. The spring constant of the cardanic ring (10) possesses a characteristic such that, starting from a maximum gap width (s) in the state of rest of the centrifugal pump, the axial gap (s) (8) close (s) under operating conditions to a minimum width at which contact between the faces delimiting the axial gap (s) (8) is still avoided.

Full Text	-1- The invention relates to a relieving device for multistage centrifugal pumps which possesses one or more axial gaps and a relieving device for multistage centrifugal pumps which possesses axial gap (8) and one or axial gaps and one or more radial gaps and in which a relieving stream is led via the gaps, and with an axial bearing absorbing the remaining residual thrust, the axial bearing being assigned a cardanic ring serving for the compensation of errors of alignment. For absorbing the axial thrust in multistage centrifugal pumps, essentially three different types of relieving devices are known: relieving disk, relieving piston and stepped piston. The latter is designed, in the form predominantly in use, as a double piston. The devices mentioned are described under the keyword "axial thrust" in the KSB Centrifugal Pump Lexicon, third edition, 1989. What is common to all three versions is a relieving stream led via gaps. The relieving stream, usually led back to the inlet of the centrifugal pump, causes a leakage loss. Therefore, attemps are made to minimize the loss by means of gap widths which are as small as possible. In this case, however, care must be taken to ensure that a rubbing of the moved parts against the stationary parts of the centrifugal pump is as far as possible avoided under all operating conditions. Rubbing of the pump rotor in the casing may lead to scoring on surfaces located opposite one another and therefore to the failure of the centrifugal pump. - 2 - The gap losses occurring in each case due to the relieving stream differ in the three versions. Thus, above all, the radial gap surrounding the single relieving piston results in a large gap stream and therefore in a sharp decrease in efficiency of the centrifugal pump. By contrast, the gap loss of a stepped-piston relieving device, which, depending on the number of steps, has at least two radial gaps and in each case an axial gap arranged between the radial gaps, is substantially lower. What is common to both versions operating with pistons is that they also require an axial bearing which absorbs a remaining residual thrust. The version with a relieving disk does not, in principle, require such an axial bearing, since the relieving disk has a self-regulating effect. Since the axial gap, appreciable here, between the relieving disk and the nonrotating counterdisk is set very narrow, the leakage loss of this version also remains relatively low. However, in centrifugal pumps with high output pressures and high powers, along with a transient mode of operation, rubbing of the relieving disk against the counterdisk may occur. Consequently, however, the operating reliability of such pumps is no longer guaranteed. The object on which the invention is based is to provide a relieving device which, along with high reliability, has only minimal leakage losses. Proceeding from a device of the type initially mentioned, the set object is achieved in that the relieving device is designed in such a way that, in all the operating states, a residual thrust occurs which acts in the direction of the suction side of the centrifugal pump, and in that the cardanic ring is dimensioned in such a way that it is deformed -3- elastically by the residual thrust, the spring constant of the cardanic ring possessing a characteristic such that, starting from a maximum gap width in the state of rest of the centrifugal pump, the axial gap closes under operating conditions to a minimum width at which contact between the faces delimiting the axial gap is still avoided. If the relieving device possesses a stepped piston with a plurality of axial gaps, the condition mentioned applied to all the axial gaps. However, the invention can be used not only in the case of relieving devices with double pistons or multistep pistons. It may also be employed in the case of relieving disks. Admittedly, an additional axial bearing with a cardanic ring entails an increased outlay in the case of a device with a relieving disk. However, since the operating reliability in centrifugal pumps with high output pressures and high powers can thereby be guaranteed even in the case of a transient mode of operation, the outlay is justified there at least. The invention can be used advantageously, about all, in cooperation with a hydrodynamic axial bearing. The invention is explained in more detail by means of an exemplary embodiment and with reference to accompanying drawing wherein fig. 1 shows a detail of a multistage centrifugal pump. Mounted in the casing 1 of the centrifugal pump is a shaft 2 which carriers a plurality of rotors 3. Only two of the rotors 3 can be seen in the drawing. Moreover, the double piston 4 of a relieving device according to the invention is fastened on the shaft 2. The double piston 4 is surrounded by a casing part 5 with which it forms two radial gaps 6 and 7. Between... - 4 - the radial gaps 6 and 7 is located an axial gap 8. The axial gap 8 has a variable width s. At the delivery-side end of the centrifugal pump, the shaft 2 is received by a hydrodynamic axial bearing 9. The axial bearing 9 is assigned a cardanic ring 10. The cardanic ring 10 serves in the first place, in a known way, for the compensation of errors of alignment which are unavoidable during the assembly of a multistage centrifugal pump. What is novel, however, is that the cardanic ring 10 is dimensioned in such a way that it is deformed elastically by the residual thrust occurring in the centrifugal pump. In this case, the spring constant of the cardanic ring 10 is adapted to the other parameters of the relieving device: The relieving device is designed in such a way that, in all the operating states of the centrifugal pump, a residual thrust occurs which acts in the direction of the suction side. Starting from a maximum width s of the axial gap 8 in the state of rest of the centrifugal pump, then, due to an elastic deformation of the cardanic ring 10 the gap 8 is closed under operating conditions to a predetermined minimum width at which contact between those faces of the double piston 4 and of the casing part 5 which delimit the gap 8 is still avoided. At the same time, a useful feature of the relieving device according to the invention is that the axial gap 8 possesses a self-regulating function, as is the case in a similar way with regard to a relieving disk. -5-WE CLAIM 1. A device for absorbing the axial thrust of a multistage centrifugal pump, with a relieving device which possesses an axial gap (8) with variable width and one or more radial gaps (6, 7) and in which a relieving stream is led via the gaps (6, 7, 8) and with an axial bearing (9) absorbing the remaining residual thrust, the axial bearing (9) being assigned a cardanic ring (10) serving for the compensation of errors of alignment, characterized in that the relieving device is designed in such a way that, in all the operating states, a residual thrust occurs which acts in the direction of the suction side of the centrifugal pump, and in that the cardanic ring (10) is dimensioned in such a way that it is deformed elastically by the residual thrust, the spring constant of the cardanic ring (10) possessing a characterized such that, starting from a maximum gap width (s) in the state of rest of the centrifugal pump, the axial gap (8) closes under operating conditions to a minimum width at which contact between the faces delimiting the axial gap (8) is still avoided. 2. A device for absorbing the axial thrust of a multistage centrifugal pump, with a relieving device which possesses a plurality of axial gaps (8) having variable width and radial gaps (6, 7, 8) and in which a relieving stream is led via the gaps (6, 7, 8) and with an axial bearing (9) absorbing the remaining residual thrust, the axial bearing (9) being assigned a cardanic ring (10) serving for the compensation of errors of alignment, characterized in that the relieving device is designed in such a way that, in all the operating states, a residual thrust occurs which acts in the direction of the suction side of the centrifugal pump, and in that the - 6 - cardanic ring (10) is dimensioned in such a way that it is deformed elastically by the residual thrust, the spring constant of the cardanic ring (10) possessing a characteristic such that, starting from a maximum gap width (s) in the state of rest of the centrifugal pump, the axial gaps close under operating conditions to a minimum width at which contact between the faces delimiting the axia1 gaps is still avoided. 3. A device as claimed in claim 1, characterized in that the relieving device is formed by a double piston (4) with an axial gap (8) located between the two piston parts. 4. The device as claimed in claim 2, characterized in that the relieving device is formed by a stepped piston in each case with an axial gap located between two steps. 5. The device as claimed in claim 1, characterized in that the relieving device is formed by a relieving disk which with a casing-side counterdisk forms an axial gap. 6. The device as claimed xn one of claims 1 to 5, characterized in that a hydrodynamic axial bearing (9) is used as an axial bearing. This invention relates to a device for absorbing the axial thrust of a multistage centrifugal pump which possesses an axial gap (8), radial gaps (6, 7), an axial bearing (9) absorbing the remaining residual thrust. The axial bearing (9) is being assigned a cardanic ring (10) serving for the compensation of errors of alignment. The relieving device is designed in such as way that, in all the operating states, a residual thrust occurs which acts in the direction of the suction side of the centrifugal pump, and in that the cardanic ring (10) is dimensioned in such a way that it is deformed elastically by the residual thrust. The spring constant of the cardanic ring (10) possesses a characteristic such that, starting from a maximum gap width (s) in the state of rest of the centrifugal pump, the axial gap (s) (8) close (s) under operating conditions to a minimum width at which contact between the faces delimiting the axial gap (s) (8) is still avoided.

Full Text

-1-

The invention relates to a relieving device for multistage centrifugal pumps which possesses one or more axial gaps and a relieving device for multistage centrifugal pumps which possesses axial gap (8) and one or axial gaps and one or more radial gaps and in which a relieving stream is led via the gaps, and with an axial bearing absorbing the remaining residual thrust, the axial bearing being assigned a cardanic ring serving for the compensation of errors of alignment.
For absorbing the axial thrust in multistage centrifugal pumps, essentially three different types of relieving devices are known: relieving disk, relieving piston and stepped piston. The latter is designed, in the form predominantly in use, as a double piston. The devices mentioned are described under the keyword "axial thrust" in the KSB Centrifugal Pump Lexicon, third edition, 1989.
What is common to all three versions is a relieving stream led via gaps. The relieving stream, usually led back to the inlet of the centrifugal pump, causes a leakage loss. Therefore, attemps are made to minimize the loss by means of gap widths which are as small as possible. In this case, however, care must be taken to ensure that a rubbing of the moved parts against the stationary parts of the centrifugal pump is as far as possible avoided under all operating conditions. Rubbing of the pump rotor in the casing may lead to scoring on surfaces located opposite one another and therefore to the failure of the centrifugal pump.

- 2 -
The gap losses occurring in each case due to the
relieving stream differ in the three versions. Thus,
above all, the radial gap surrounding the single
relieving piston results in a large gap stream and
therefore in a sharp decrease in efficiency of the
centrifugal pump. By contrast, the gap loss of a
stepped-piston relieving device, which, depending on
the number of steps, has at least two radial gaps and
in each case an axial gap arranged between the radial
gaps, is substantially lower. What is common to both
versions operating with pistons is that they also
require an axial bearing which absorbs a remaining
residual thrust.
The version with a relieving disk does not, in principle, require such an axial bearing, since the relieving disk has a self-regulating effect. Since the axial gap, appreciable here, between the relieving disk and the nonrotating counterdisk is set very narrow, the
leakage loss of this version also remains relatively low. However, in centrifugal pumps with high output pressures and high powers, along with a transient mode of operation, rubbing of the relieving disk against the counterdisk may occur. Consequently, however, the
operating reliability of such pumps is no longer guaranteed.
The object on which the invention is based is to provide a relieving device which, along with high reliability, has only minimal leakage losses.
Proceeding from a device of the type initially mentioned, the set object is achieved in that the relieving device is designed in such a way that, in all the operating states, a residual thrust occurs which acts in the direction of the suction side of the centrifugal pump, and in that the cardanic ring is dimensioned in such a way that it is deformed

-3-
elastically by the residual thrust, the spring constant of the cardanic ring possessing a characteristic such that, starting from a maximum gap width in the state of rest of the centrifugal pump, the axial gap closes under operating conditions to a minimum width at which contact between the faces delimiting the axial gap is still avoided. If the relieving device possesses a stepped piston with a plurality of axial gaps, the condition mentioned applied to all the axial gaps.
However, the invention can be used not only in the case of relieving devices with double pistons or multistep pistons. It may also be employed in the case of relieving disks. Admittedly, an additional axial bearing with a cardanic ring entails an increased outlay in the case of a device with a relieving disk. However, since the operating reliability in centrifugal pumps with high output pressures and high powers can thereby be guaranteed even in the case of a transient mode of operation, the outlay is justified there at least.
The invention can be used advantageously, about all, in cooperation with a hydrodynamic axial bearing.
The invention is explained in more detail by means of an exemplary embodiment and with reference to accompanying drawing wherein fig. 1 shows a detail of a multistage centrifugal pump.
Mounted in the casing 1 of the centrifugal pump is a shaft 2 which carriers a plurality of rotors 3. Only two of the rotors 3 can be seen in the
drawing.
Moreover, the double piston 4 of a relieving device according to the invention is fastened on the shaft 2. The double piston 4 is surrounded by a casing part 5 with which it forms two radial gaps 6 and 7. Between...

- 4 -
the radial gaps 6 and 7 is located an axial gap 8. The axial gap 8 has a variable width s.
At the delivery-side end of the centrifugal pump, the shaft 2 is received by a hydrodynamic axial bearing 9. The axial bearing 9 is assigned a cardanic ring 10. The cardanic ring 10 serves in the first place, in a known way, for the compensation of errors of alignment which are unavoidable during the assembly of a multistage
centrifugal pump. What is novel, however, is that the cardanic ring 10 is dimensioned in such a way that it is deformed elastically by the residual thrust occurring in the centrifugal pump. In this case, the spring constant of the cardanic ring 10 is adapted to
the other parameters of the relieving device:
The relieving device is designed in such a way that, in
all the operating states of the centrifugal pump, a
residual thrust occurs which acts in the direction of
the suction side. Starting from a maximum width s of
the axial gap 8 in the state of rest of the centrifugal
pump, then, due to an elastic deformation of the
cardanic ring 10 the gap 8 is closed under operating
conditions to a predetermined minimum width at which
contact between those faces of the double piston 4 and
of the casing part 5 which delimit the gap 8 is still
avoided. At the same time, a useful feature of the
relieving device according to the invention is that the
axial gap 8 possesses a self-regulating function, as is
the case in a similar way with regard to a relieving
disk.

-5-WE CLAIM
1. A device for absorbing the axial thrust of a multistage centrifugal pump, with a relieving device which possesses an axial gap (8) with variable width and one or more radial gaps (6, 7) and in which a relieving stream is led via the gaps (6, 7, 8) and with an axial bearing (9) absorbing the remaining residual thrust, the axial bearing (9) being assigned a cardanic ring (10) serving for the compensation of errors of alignment, characterized in that the relieving device is designed in such a way that, in all the operating states, a residual thrust occurs which acts in the direction of the suction side of the centrifugal pump, and in that the cardanic ring (10) is dimensioned in such a way that it is deformed elastically by the residual thrust, the spring constant of the cardanic ring (10) possessing a characterized such that, starting from a maximum gap width (s) in the state of rest of the centrifugal pump, the axial gap (8) closes under operating conditions to a minimum width at which contact between the faces delimiting the axial gap (8) is still avoided.
2. A device for absorbing the axial thrust of a multistage centrifugal pump, with a relieving device which possesses a plurality of axial gaps (8) having variable width and radial gaps (6, 7, 8) and in which a relieving stream is led via the gaps (6, 7, 8) and with an axial bearing (9) absorbing the remaining residual thrust, the axial bearing (9) being assigned a cardanic ring (10) serving for the compensation of errors of alignment, characterized in that the relieving device is designed in such a way that, in all the operating states, a residual thrust occurs which acts in the direction of the suction side of the centrifugal pump, and in that the

- 6 -
cardanic ring (10) is dimensioned in such a way that it is deformed elastically by the residual thrust, the spring constant of the cardanic ring (10) possessing a characteristic such that, starting from a maximum gap width (s) in the state of rest of the centrifugal pump, the axial gaps close under operating conditions to a minimum width at which contact between the faces delimiting the axia1 gaps is still avoided.
3. A device as claimed in claim 1, characterized in
that the relieving device is formed by a double
piston (4) with an axial gap (8) located between
the two piston parts.

4. The device as claimed in claim 2, characterized in
that the relieving device is formed by a stepped
piston in each case with an axial gap located
between two steps.

5. The device as claimed in claim 1, characterized in
that the relieving device is formed by a relieving
disk which with a casing-side counterdisk forms an
axial gap.

6. The device as claimed xn one of claims 1 to 5,
characterized in that a hydrodynamic axial bearing
(9) is used as an axial bearing.
This invention relates to a device for absorbing the axial thrust of a multistage centrifugal pump which possesses an axial gap (8), radial gaps (6, 7), an axial bearing (9) absorbing the remaining residual thrust. The axial bearing (9) is being assigned a cardanic ring (10) serving for the compensation of errors of alignment. The relieving device is designed in such as way that, in all the operating states, a residual thrust occurs which acts in the direction of the suction side of the centrifugal pump, and in that the cardanic ring (10) is dimensioned in such a way that it is deformed elastically by the residual thrust. The spring constant of the cardanic ring (10) possesses a characteristic such that, starting from a maximum gap width (s) in the state of rest of the centrifugal pump, the axial gap (s) (8) close (s) under operating conditions to a minimum width at which contact between the faces delimiting the axial gap (s) (8) is still avoided.

Documents:

in-pct-2001-01107-kol abstract.pdf

in-pct-2001-01107-kol claims.pdf

in-pct-2001-01107-kol correspondence.pdf

in-pct-2001-01107-kol description(complete).pdf

in-pct-2001-01107-kol drawings.pdf

in-pct-2001-01107-kol form-1.pdf

in-pct-2001-01107-kol form-18.pdf

in-pct-2001-01107-kol form-2.pdf

in-pct-2001-01107-kol form-26.pdf

in-pct-2001-01107-kol form-3.pdf

in-pct-2001-01107-kol form-5.pdf

in-pct-2001-01107-kol letters patent.pdf

in-pct-2001-01107-kol priority document others.pdf

IN-PCT-2001-1107-KOL-(13-12-2011)-CORRESPONDENCE.pdf

IN-PCT-2001-1107-KOL-(13-12-2011)-PA-CERTIFIED COPIES.pdf

IN-PCT-2001-1107-KOL-FORM 27.pdf

IN-PCT-2001-1107-KOL-FORM-27-1.1.pdf

IN-PCT-2001-1107-KOL-FORM-27.pdf

in-pct-2001-1107-kol-granted-abstract.pdf

in-pct-2001-1107-kol-granted-claims.pdf

in-pct-2001-1107-kol-granted-correspondence.pdf

in-pct-2001-1107-kol-granted-description (complete).pdf

in-pct-2001-1107-kol-granted-drawings.pdf

in-pct-2001-1107-kol-granted-form 1.pdf

in-pct-2001-1107-kol-granted-form 18.pdf

in-pct-2001-1107-kol-granted-form 2.pdf

in-pct-2001-1107-kol-granted-form 26.pdf

in-pct-2001-1107-kol-granted-form 3.pdf

in-pct-2001-1107-kol-granted-form 5.pdf

in-pct-2001-1107-kol-granted-letter patent.pdf

in-pct-2001-1107-kol-granted-reply to examination report.pdf

in-pct-2001-1107-kol-granted-specification.pdf

in-pct-2001-1107-kol-granted-translated copy of priority document.pdf

« Previous Patent

Next Patent »

Patent Number

213440

Indian Patent Application Number

IN/PCT/2001/1107/KOL

PG Journal Number

01/2008

Publication Date

04-Jan-2008

Grant Date

02-Jan-2008

Date of Filing

19-Oct-2001

Name of Patentee

KSB AKTIENGESELLSCHAFT

Applicant Address

JOHANN-KLEIN - STRASSE 9, D-67227, FRANKENTHAL

Inventors:

#	Inventor's Name	Inventor's Address
1	WANG, BAOGANG	WELSCHGASSE 21, D-67227, FRANKENTHAL
2	BRECHT,BERNHARD	OTTO-DILL-STRASSE 5, D-67227 FRANKENTHAL
3	SCHILL , JURGEN	BACHWEG 10, D-67273 WEISENHEIM AM BEFG

PCT International Classification Number

F 04 D 29/04

PCT International Application Number

PCT/EP00/04754

PCT International Filing date

2000-05-25

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	DE 199 27 135.6	1999-06-15	Germany