[0001] The present invention relates to a locking device for locking the stator pack of
submersible centrifugal pumps.
[0002] Said device is suitable for locking the pack of the diffusers preventing the pack
from moving inside the cylindrical shell of the pump, particularly along an axial
direction.
[0003] Italian patent
IT 1005473, filed in the name of the same applicant, discloses a locking device comprising a
pair of end crowns each of which is fixed inside the cylindrical shell, respectively
upstream and downstream the stator pack, by means of an elastic ring having circular
section and toroidal shape inserted into a corresponding groove obtained inside said
shell. Each crown is provided with threaded holes suitable for receiving respective
screws passing through closing flanges arranged at opposite ends of the shell and
centred thereon. The crown arranged downstream the stator pack acts as an axial stop
for the pack, while the crown arranged upstream the pack acts as a fastening element
for the upper flange. The upper flange abuts on a collar provided with a step centring
and abutting the collar on a peripheral region of the first diffuser of the pack.
In this manner, when the upper flange is fixed to the respective crown by means of
the screws, the stator pack is tightened between the collar and the crown arranged
at the opposite end. In a variation, said device comprises a crown which is welded
at an end of the pump shell and is not fixed to the shell by means of elastic ring.
[0004] A drawback of the devices of this type is that, when the flanges are fixed to the
shell by means of the screws, the tightening torque has to be limited to a pre-established
value for preventing the elastic ring from being extruded into the space existing
between the crown and the shell so as to deform the groove and bend the shell, or
even exiting from the groove.
[0005] While the pump is working, then, the elastic ring is stressed not only by the stresses
caused by the tightening of the screws, but also by the pressure of the liquid, so
that such locking device is may be applied only to pumps having limited head and small
number of stages.
[0006] Since the internal diameter of the shell, the external diameter of the crown and
the groove arranged for receiving the elastic ring are subjected to size variations
due to manufacturing tolerances, the tightening torque of the screws must have a limited
value for preventing dangerous ejection of the ring from the seat thereof in condition
of maximum clearance.
[0007] Furthermore, a locking device is known comprising two rows of slots punched in the
outer cylindrical shell of the pump on two planes parallel to each other and orthogonal
to the axis of the pump, arranged respectively upstream and downstream the stator
pack.
[0008] Through said slots, nibs may be introduced into the shell, said nibs being provided
on nuts which are capable of engaging the threaded ends of tie rods arranged parallelly
to the axis of the pump and passing through holes obtained in the closing flanges
of the pump. The above-mentioned nibs act as stops for the end diffusers of the stator
pack so allowing said diffusers to be locked.
[0009] In a further version the pump may comprise a flange welded at one end thereof and
a device analogous to the above-described device at the other end. Examples of the
afore said locking device are disclosed in KSB's catalogue (on pages 11-14 and 33-36),LEBA's
catalogue (on pages 1-14),HYDROPOMPE WS's catalogue (on page 11).
[0010] A drawback of such devices consists in that punching or shearing the slots on the
external shell produces out-of-round deformations of the shell which makes it difficult
to introduce the pack into the shell and requires onerous operations of adjustment.
[0011] Furthermore, shearing the above-mentioned slots hardens the steel which the shell
is made of so promoting starting of corrosion.
[0012] The tightening stress, furthermore, is not uniformly distributed on the circumferential
edge of the shell, but is concentrated in regions from which cracks and corrosion
under fatigue start.
[0013] Eventually, the assembly of a locking device of such type, i.e. provided with a special
reference nut, is rather complex and such to require a high loss of time.
[0014] Furthermore, a locking device is known comprising a pair of flanges, each arranged
at one of the ends of the shell, which protrude from said shell and are provided with
holes arranged externally with respect to the diameter of the shell and suitable for
allowing tie rods to be housed. On the threaded ends of such tie rods nuts are engaged
which tighten the shell, and consequently the stator pack, between the flanges of
the pump. A variation consists in the absence of an external metallic shell and the
use of diffusers each provided with its own shell. Examples of the afore said locking
device are disclosed in KSB's catalogue (on pages 23-26),EBARA's catalogue (on papes
1-15),ITT-LOWARA's catalogue of Z612/Z616/Z622/Z631/Z646/Z660 Series (on pages 1-54).
[0015] Devices of this type are very bulky and considerably increase the radial overall
dimensions due to the presence of the tie rods, which are sized according to the maximum
pressure exerted by the pump during working.
[0016] Furthermore, devices of this type are uneconomic since, when a single external metallic
shell is used, the shell carries out only a function of containment of the diffusers
and it is necessary to further provide a plurality of axial tie rods arranged for
bearing axial compression of said diffusers.
[0017] Finally, a locking device is known comprising a pair of flanges threaded on their
external diameter and each arranged at one of the ends of the shell. The threads of
said flanges engage a respective threaded section obtained on the internal surface
of the shell. The stator pack of the diffusers is locked by screwing to the shell
the two treaded flanges. In a version of the above-mentioned device, the shell comprises
a
[0018] first flange welded at one end thereof and suitable for acting as a stop for the
first diffuser of the pack and a second threaded flange screwed at the other end.
Examples of the afore said locking device are disclosed in HYDROPOMPE WS's catalogue
(on pages 9),IIT-LOWARA's catalogue of SCUBA/GS Series (on pages 1-35),NUOVA STAA
POMPE's catalogue (on pages 34-49).
[0019] In devices of this type, however, it is rather difficult to obtain high tightening
torques; consequently it is not always possible to give to the pack of the diffusers
the desired pressure.
[0020] In addition, high tightening torques are difficult to be obtained because the shell
and the flange are made of similar material, which involves high risks of seizing
during screwing.
[0021] Furthermore, pumps provided with such devices are difficult to be disassembled due
to the presence of encrusting material, such as sludge or slime, which may accumulate
at the threaded coupling.
[0022] US 4171934 discloses a submergible electric pump comprising a discharge head provided with a
locking device for locking the discharge head to a well liner, the device comprising
a plurality of lugs projected into a groove in the well liner when the pump is lowered
through the liner to an operative position, at which, the discharge head is sealed
in the liner. The discharge head has inner and outer tubular members, the outer member
seating on the liner and being held against rotation relative to the liner. The inner
member continues to move downwardly after the outer member is seated, camming the
locking lugs outwardly through windows in the outer member and into the liner groove.
The lugs provide support for the weight of the pump installation and prevent rotation
between the inner and outer members of the discharge head.
[0023] EP 0610826 discloses a centrifugal pump of the type comprising a supporting body (10) for a
permanent-magnet synchronous motor with an impeller (49) coupled to its rotor (22),
and for a volute (48) in which the impeller is accommodated. The body (10) and the
volute (48) form a sealed housing containing the rotor and the impeller in respective
chambers, separating them from the stator part of the motor. The rotor (22) is rigidly
coupled to a shaft (24) rotating on sliding bearings (26, 29) supported by elastic
supports locked in the corresponding chamber, one of which supports forms a ring for
providing hydraulic sealing between the two chambers of the container.
[0024] US 4445820 discloses an electrically powered pump, in which the armature of the motor is rotatably
fitted through the bearings provided at both ends of its rotary shaft. A rotor is
rotatably mounted through a fixed shaft arranged differently from the rotary shaft
to form a pump means, the rotary shaft and the rotor being connected by a connector
means in such a manner that the radial displacement of both axes of the rotary shaft
and the rotor can be absorbed by the connector. In another embodiment, two stages
of impellers are rotatably mounted to the fixed shaft arranged in axially alignment
with the rotary shaft to form a pump means. The rotary shaft and the impellers are
connected by a connector means in such a manner that the relative motion in a circumferential
direction of the rotary shaft and the impellers is restricted.
[0025] An object of the present invention is to improve the known locking devices.
[0026] Another object of the present invention is to provide a device for locking the stator
pack of a pump comprising an elastic ring which is easy to be inserted into and extracted
from a respective seat.
[0027] A further object of the invention is to provide a locking device comprising an elastic
ring which is substantially free from deformations during working, so that the risk
of an ejection of the ring from the groove in which it is housed is reduced.
[0028] According to the invention, a submersible centrifugal pump is provide as defined
in claim 1.
[0029] Advantageously, said elastic ring means comprises tooth means suitable for engaging
respective groove means obtained in said shell means.
[0030] In such manner, a pre-established axial position in said shell for said elastic ring
means is provided.
[0031] Preferably, said friction surface is a conical surface. Advantageously, moreover,
the ring means is broken in a section of the peripheral edge thereof, which allows
a limited circumferential deformation, however sufficient to allow the tooth means
to firmly engage the groove means obtained in the shell.
[0032] Further advantageously, said flange means is associated with support means provided
with a support step which engages the first of the diffusers of the pack of the pump.
Therefore, when the screws are tightened, the flange means presses the support means
which locks the stator pack of the pump so preventing any movement thereof.
[0033] Owing to the present invention it is possible to obtain a device in which the locking
action is obtained by coupling friction surfaces arranged for mutually locking. The
wedge means, therefore, act as axially rigid elements so preventing the risk of ejection.
[0034] Furthermore, since the tooth means, in a working condition, are mainly stressed on
the surfaces arranged perpendicularly to the axis of the shell, no force component
acts on said tooth means promoting said tooth means to exit from the respective groove
means.
[0035] Owing to the present invention, eventually, it is possible to produce a locking device
for locking a stator pack which may be used also in pumps of high head, or in any
case also in pumps for which at this moment the solution disclosed in
IT 1005473 is not suitable due to the high hydraulic internal pressure.
[0036] The invention can be better understood and carried out with reference to the enclosed
drawings which show some exemplifying and not restrictive embodiments thereof, in
which:
Figure 1 is a longitudinal broken section of a pump provided with a locking device
according to the invention;
Figure 2 is an enlarged detail of Figure 1;
Figure 3 is a further enlarged detail of Figure 1 which shows an elastic ring inserted
into a respective seat;
Figure 4 is a section taken along the plane IV-IV of Figure 2 which shows the elastic
ring in the region in which it is broken.
[0037] With reference to Figures 1 to 3, a pump 1 is shown comprising an external shell
2 consisting of a steel tubular element into which a crown 3 is housed.
[0038] Between the crown 3 and the shell 2 an elastic ring 4 is arranged comprising a protruding
portion 5 arranged for being housed into a groove 6 obtained in the shell 2. The elastic
ring 4 comprises a conical surface section 7 suitable for being coupled with a respective
conjugate surface 7a of the crown 3.
[0039] The pump 1 further comprises a closing flange 8 suitable for closing the shell 2
which is fixed to the crown 3 by means of screws 9 engaging threaded holes obtained
in the above-mentioned crown 3.
[0040] While the screws 9 are tightened, the ring means 4 are kept firmly connected to the
shell 2 because the protruding portion 5 couples with the groove 6, while the crown
3 moves towards the flange 8 bringing the conjugate surfaces 7 and 7a to keep in contact
with each other.
[0041] With reference to Figure 4, an inclined cut 15 breaking the circumference of the
ring 4 is shown; the above-mentioned cut 15 allows the ring 4 to be the quickly removed
using a standard flat-end screwdriver when the pump 1 is disassembled. The cut 15
allows the ring 4 to deform so as to allow the protruding portion 5 to be housed into
the groove 6.
[0042] Since during working the ring 4 does not lock the crown 3 owing to an elastic deformation,
but rather locks the crown 3 by substantially acting as a body rigidly fixed to the
shell 2, advantageously the ring 4 is made of steel for a better stress strength.
[0043] With reference again to Figures 1 to 3, impellers 10, keyed onto the shaft 11 and
fixed thereto through a further screw 16, and the diffusers 12 are further arranged
internally to the shell 2.
[0044] The flange 8 comprising the valve body of the pump 1 abuts on a support 13 provided
with a step 14 which engages the first diffuser 12 so locking said diffuser 12 and
the whole stator pack of the pump 1 and, therefore, preventing the stator pack from
sliding in an axial direction.
[0045] The pump 1 is provided, in the not-shown portion arranged downstream the stator pack,
with a further crown, provided with a further ring similar to the above-described
ring, said crown acting as a supporting and stopping element for the stator pack.
[0046] In another not-shown version, the crown arranged downstream the stator pack, is not
fixed to the shell by means of an elastic ring, but is directly welded to said shell.
[0047] The pump is assembled in the way described hereinafter.
[0048] The impellers 10 and the diffusers 12, alternated in a suitable sequence, are inserted
on the shaft 11 abutting, at the bottom, on the driving joint of the shaft 11, not
shown, and being tightened, at the top, with the screw 16 which engages a threaded
hole obtained in the upper end of the shaft 11.
[0049] The pack so assembled is then inserted into the shell 2 until it abuts on the lower
crown, not shown, fixed to the shell by elastic ring 4, or by welding.
[0050] Subsequently, the sub-group of the support 13 is inserted into the shell 2 and then
the crown 3 is introduced and pushed until it contacts the shoulder of the support
13 for allowing the groove 6 obtained in the shell 2 to become accessible. Then the
elastic ring 4 is inserted into the shell 2 until the protruding portion 5 thereof
engages the groove 6 obtained in the shell 2.
[0051] The flange 8, comprising the stop valve, is placed on the upper end of the shell
2, so that the holes present on the flange 8 are properly aligned with the threaded
holes present on the crown 3 previously inserted into the shell 2.
[0052] At this point the screws 9 are inserted into the respective holes and are screwed
into the threaded holes of the crown 3 until the value of the pre-established tightening
torque is reached; during this operation the crown 3 rises so engaging the elastic
ring 4. In a first phase, the surface 7a of the crown 3 slides on the conjugated surface
7 of the ring 4, expanding the ring 4 until the protruding portion 5 perfectly adheres
to the internal surface of the groove 6; in the second phase, once the ring 4 has
reached the lower stop at the end of the inclined surface 7a of the crown 3, the very
stage of pre-loading the hydraulic pack begins until the closing flange 8 reaches
the shoulder at the upper edge of the shell 2.
[0053] In a variation of the described tightening device the flange 8 does not reach the
shoulder on the upper edge of the shell 2: in this case the axial load on the pack
is obtained tightening the screws 9 until the pre-established tightening torque is
reached.
1. Submersible centrifugal pump (1), having a locking device for locking the stator pack
of said pump (1), comprising shell means (2) suitable for containing pumping stages
for pumping a fluid, crown means (3) provided with connecting and fixing means (9)
arranged for connecting flange means (8) of said pump (1) to said crown means (3),
said flange means (8) being suitable for hermetically closing said shell means (2),
elastic ring means (4) arranged between said shell means (2) and said crown means
(3), suitable for preventing said crown means (3) from sliding in an axial direction
inside said shell means (2), characterized in that, said elastic ring means (4) comprises wedge means provided with a friction surface
(7) suitable for being coupled with a respective conjugate surface (7a) of said crown
means (3).
2. Pump according to claim 1, wherein said friction surface is a conical surface (7).
3. Pump according to claim 1, or 2, wherein said elastic ring means (4) comprises tooth
means (5) suitable for engaging respective groove means (6) obtained in said shell
means (2).
4. Pump according to claim 3, wherein said elastic ring means (4) comprises a cut (15)
in a section of a peripheral edge thereof suitable for allowing said elastic ring
means (4) to deform in a circumferential direction for allowing said tooth means (5)
to engage said groove means (6).
5. Pump according to any preceding claim, wherein said elastic ring means (4) are made
of steel.
6. Pump according to any preceding claims, wherein said flange means (8) is associated
with support means (13) suitable for engaging an end diffuser (12) of said stator
pack for preventing said stator pack from moving in an axial direction inside said
shell (2).
1. Tauchzentrifugalpumpe (1), die eine Verriegelungsvorrichtung zum Verriegeln des Statorpakets
der Pumpe (1) aufweist, mit Schalenmitteln (2), die dazu geeignet sind, Pumpstufen
zum Pumpen eines Fluids zu enthalten, Kronenmitteln (3), die mit Verbindungs- und
Befestigungsmitteln (9) versehen sind, die zum Verbinden von Flanschmitteln (8) der
Pumpe (1) mit den Kronenmitteln (3) ausgelegt sind, wobei die Flanschmittel (8) dazu
geeignet sind, die Schalenmittel (2) hermetisch zu verschließen, wobei elastische
Ringmittel (4) zwischen den Schalenmitteln (2) und den Kronenmitteln (3) angeordnet
sind, die dazu geeignet sind, zu verhindern, dass die Kronenmittel (3) in einer axialen
Richtung innerhalb der Schalenmittel (2) gleiten, dadurch gekennzeichnet, dass die elastischen Ringmittel (4) Keilmittel aufweisen, die mit einer Reiboberfläche
(7) versehen sind, die dazu geeignet ist, mit einer entsprechenden konjugierten Oberfläche
(7a) der Kronenmittel (3) gekoppelt zu werden.
2. Pumpe nach Anspruch 1, wobei die Reiboberfläche eine konische Oberfläche (7) ist.
3. Pumpe nach Anspruch 1 oder 2, wobei die elastischen Ringmittel (4) Zahnmittel (5)
aufweisen, die dazu geeignet sind, mit entsprechenden Nutmitteln (6) in Eingriff zu
kommen, die in den Schalenmitteln (2) enthalten sind.
4. Pumpe nach Anspruch 3, wobei die elastischen Ringmittel (4) einen Ausschnitt (15)
in einem Abschnitt eines Umfangsrandes derselben aufweisen, der geeignet ist, dass
die elastischen Ringmittel (4) sich in einer Umfangsrichtung verformen können, damit
die Zahnmittel (5) mit den Nutmitteln (6) in Eingriff kommen.
5. Pumpe nach einem der vorhergehenden Ansprüche, wobei die elastischen Ringmittel (4)
aus Stahl gefertigt sind.
6. Pumpe nach einem der vorhergehenden Ansprüche, wobei den Flanschmitteln (8) Stützmittel
(13) zugeordnet sind, die dazu geeignet sind, mit einem Enddiffusor (12) des Statorpakets
in Eingriff zu kommen, um zu verhindern, dass das Statorpaket sich in einer axialen
Richtung innerhalb der Schale (2) bewegt.
1. Pompe centrifuge submersible (1), pourvue d'un dispositif de blocage pour bloquer
le bloc stator de ladite pompe (1), comprenant des moyens de corps (2) aptes à contenir
des étages de pompage pour le pompage d'un fluide, des moyens de couronne (3) pourvus
de moyens de raccord et de fixation (9), agencés de manière à raccorder des moyens
de bride (8) de ladite pompe (1) auxdits moyens de couronne (3), lesdits moyens de
bride (8) étant aptes à fermer hermétiquement lesdits moyens de corps (2), des moyens
de bague élastique (4) placés entre lesdits moyens de corps (2) et lesdits moyens
de couronne (3), aptes à empêcher lesdits moyens de couronne (3) de glisser dans une
direction axiale à l'intérieur desdits moyens de corps (2), caractérisée en ce que lesdits moyens de bague élastique (4) comprennent des moyens de cale pourvus d'une
surface de frottement (7) apte à être couplée avec une surface conjuguée respective
(7a) desdits moyens de couronne (3).
2. Pompe selon la revendication 1, dans laquelle ladite surface de frottement est une
surface conique (7).
3. Pompe selon la revendication 1 ou 2, dans laquelle lesdits moyens de bague élastique
(4) comprennent des moyens de dent (5) aptes à engager des moyens de rainure respectifs
(6) ménagés dans lesdits moyens de corps (2).
4. Pompe selon la revendication 3, dans laquelle lesdits moyens de bague élastique (4)
comprennent une découpe (15) dans une section d'un rebord périphérique de ceux-ci,
aptes à permettre auxdits moyens de bague élastique (4) de se déformer dans une direction
circonférentielle pour permettre auxdits moyens de dent (5) d'engager lesdits moyens
de rainure (6).
5. Pompe selon l'une quelconque des revendications précédentes, dans laquelle lesdits
moyens de bague élastique (4) sont faits d'acier.
6. Pompe selon l'une quelconque des revendications précédentes, dans laquelle lesdits
moyens de bride (8) sont associés à des moyens de support (13) aptes à engager un
diffuseur (12) d'extrémité dudit bloc stator pour empêcher ledit bloc stator de se
déplacer dans une direction axiale à l'intérieur dudit corps (2).