HK1160907B - Compression device for the stator unit of a pump - Google Patents

Description

Compression device for a stator unit of a pump

Technical Field

The invention relates to a device for compressing a stator unit of a pump, which is particularly suitable for use in a multistage centrifugal pump for a well. As shown in fig. 1, a multistage centrifugal pump a of known type comprises a tubular casing B comprising a stator unit C, typically consisting of a plurality of stages stacked on top of each other.

Background

In order to prevent the pumped fluid from leaking between one stage and another, it is necessary to compress the stator unit in order to connect the stages and ensure tightness.

According to the known art, the above compression is achieved by a tubular element D, one end E of which is arranged against the stator unit C and which is provided with an apertured flange F.

The tubular housing B is also provided with a transverse through opening G suitable for housing a corresponding shaped element H provided with threaded holes arranged to align with the holes in the flange of the tubular element when the shaped element is inserted in the opening.

Such shaped elements are placed on the edges of the opening so as to remain axially constrained by the tubular casing.

Such shaped elements, as well as the flanges of the tubular elements, are connected by corresponding screws L which, when screwed in, push the tubular elements against the stator unit, thus compressing the latter.

A disadvantage of this known technique is that the compression force of the stator unit is supported by the edges of the transverse opening with reduced surface.

Therefore, even if the technique is suitable when the compression forces remain below a given limit beyond which the transverse openings will collapse (collaps), causing a loss of compression of the stator unit and therefore the aforementioned leakage, which will affect the performance of the pump.

Due to the compression losses described above, the stages may also be set into rotation by the pumped fluid, thereby damaging the pump to the extent that it may need to be replaced.

Since the required compression force increases substantially in proportion to the pump head, it should be clear that the above-mentioned known technique is suitable for pumps where the maximum head is below a given limit.

In order to overcome these drawbacks, according to another known technique (not shown here), the compression force is supported by means of a resilient locking ring housed inside an annular seat formed inside the tubular casing.

When the elastic locking ring is at rest, its outer diameter is greater than the minimum diameter of the seat, so that it can be introduced into the tubular housing and then expand at the level of this seat.

The compression of the stator unit is achieved using a thrust unit interposed between the elastic locking ring and the stator unit, and the thrust unit can be expanded in the axial direction so as to compress the stator unit.

The compression force is released on the locking ring and on the annular seat, whose surface is much greater than the surface of the edge of the transverse opening present in the above-mentioned known art.

This technique therefore makes it possible to distribute the compressive stresses on the tubular casing in a more uniform manner than the previous solutions, thus avoiding any deformation of the tubular casing.

However, this second technique has some drawbacks.

In fact, to avoid oxidation of the elastic locking ring over time, the elastic locking ring must be made of stainless steel, which, however, reduces the elasticity.

Therefore, in order to obtain a resilient locking ring that can be inserted into the tubular casing and can be continuously expanded in the respective seating portion, it is necessary to limit the deformation of the resilient locking ring required for introducing the latter into the seating portion, or alternatively, to limit the thickness of the resilient locking ring.

However, the reduced thickness of the elastic locking ring is capable of withstanding reduced compression forces and, as mentioned above, can be used in pumps where the maximum head is below a given limit.

In fact, a higher compression force will cause an axial deformation of the elastic locking ring, which may leave the seat.

Therefore, in these cases, the thickness of the elastic locking ring needs to be increased.

However, as mentioned above, this requires the use of a resilient locking ring having an outer diameter at rest that is slightly larger than the inner diameter of the seat portion, to avoid excessive radial compression of the locking ring during insertion, which would plastically deform the locking ring and render it unusable.

However, in this case, there is a disadvantage in that: the available resting surface defined by the seat, which comprises between the outer diameter of the elastic locking ring at rest and the inner diameter of the seat, is reduced, which in any case limits the applied compression force.

The present invention is intended to overcome the disadvantages of the known art as described above.

Disclosure of Invention

In particular, it is an object of the present invention to provide a device for compressing a stator unit of a pump that is more efficient and more reliable than the known types of devices described above.

The above object is achieved by a compression device for a stator unit of a compression pump, comprising:

a tubular housing defining a longitudinal axis and adapted to house the stator unit in a predetermined assembly position;

locking a ring;

-constraining means adapted to constrain said locking ring inside said tubular housing in the direction of said longitudinal axis;

a thrust unit provided with a reference surface that can be placed against said locking ring, said thrust unit being adapted to expand in an expansion direction perpendicular to said reference surface, so as to push one end of said stator unit when arranged in said assembly position;

characterized in that said thrust compression means comprises:

a reaction element capable of placing a thrust force against the locking ring on a side opposite the thrust unit;

connecting means for connecting the reaction elements to the thrust unit, the connecting means being adapted to move the reaction elements towards the thrust unit so as to arrange them against opposite sides of the locking ring.

The same object is also achieved by a pump comprising a compression device according to the invention and a stator unit adapted to be inserted into the tubular housing of the compression device against the thrust unit.

Further features and details of the invention are described in the corresponding dependent claims.

Advantageously, the invention enables the use of a thinner elastic locking ring than is required in pumps of the known type, while it enables the same compression force to be achieved.

Advantageously, the thinner elastic locking ring has a very good elasticity and is therefore able to couple with seats having a large resting surface.

Still advantageously, the present invention does not require the manufacture of an opening in the tubular housing of the pump.

Drawings

The objects and advantages, as well as others which will better emerge hereinafter, will be explained in detail in the description of preferred embodiments of the invention, provided by way of non-limiting example, with reference to the accompanying drawings, in which:

figure 1 shows a longitudinal section of a pump according to the prior art;

figure 2 shows a cross section of a pump as subject of the invention;

FIG. 3 shows a detail of FIG. 2;

fig. 4 shows an exploded isometric view of some components of the pump of fig. 2.

Detailed Description

A part of the pump of the present invention is shown in fig. 2, in which reference numeral 1 indicates the pump in its entirety.

The pump 1 is provided with a compression device 2, the compression device 2 comprising a tubular housing 3 defining a longitudinal axis X and serving as an outer jacket of the pump 1.

A stator unit 17 is arranged concentrically inside the tubular casing 3, said stator unit being composed of a plurality of stacked stages 17a and a rotor unit 18, the rotor unit 18 being connected to a shaft 19, the shaft 19 (not shown, but known per se) being operatively associated with a transmission device adapted to set the rotor unit 18 in rotation about the longitudinal axis X.

The compression device 2 further comprises a locking ring 5, the locking ring 5 being associable with the inner surface 15 of the tubular casing 3 by constraining means 4, the constraining means 4 constraining the locking ring 5 in the direction of the longitudinal axis X so that the locking ring 5 faces the stator unit 17.

The invention also comprises a thrust unit 7 arranged between the locking ring 5 and the stator unit 17.

The thrust unit 7 is provided with a reference surface 12a, the reference surface 12a being positioned against the locking ring 5 and also being expandable in an expansion direction Y perpendicular to the above-mentioned reference surface 12a, the reference surface 12a being preferably parallel to the longitudinal axis X during operation.

The expansion of the thrust unit 7 enables one end of the stator unit 17 to be pushed along the longitudinal axis X, so that the stator unit, constrained at the opposite end by the tubular casing 3, is compressed.

The compression device 2 further comprises a reaction element 8 placed against the locking ring 5 on the side opposite to the thrust unit 7.

The reaction elements 8 are associated with the thrust units 7 by means of connection means 9, the connection means 9 being adapted to move the reaction elements 8 towards the thrust units 7, preferably in a direction parallel to the longitudinal axis X, in such a way as to arrange them against respective opposite lateral faces of the locking ring 5.

The approach of the reaction element 8 towards the thrust unit 7 causes the locking ring 5 to be locked between them, reinforcing the locking ring 5 and preventing its axial deformation.

The deformation of the locking ring 5 is therefore less than in compression devices used in pumps of known type, thanks to the same compression force exerted on the stator unit 17, thus achieving the object of the invention. Further, the compression force corresponding to the predetermined deformation of the locking ring 5 exceeds the compression force required in the known art, so that the thickness of the locking ring 5 is not changed.

Advantageously, therefore, the locking ring 5 can be used in such pumps: the pump is provided with a plurality of stages which is greater than the number of stages allowed in the known art for the same number of rings.

Preferably, but not necessarily, the connection means 9 comprise screw means 10, 10 a.

In particular, as shown in greater detail in figure 3, the above-mentioned threaded means comprise a first screw 10 arranged inside the locking ring 5 and passing through the reaction element 8, which is adapted to be associated with a nut 10a in the thrust unit 7.

In a variant embodiment of the invention (not shown here), the first screw 10 may form a single body together with the reaction element 8.

The reaction element 8 is preferably a shaped washer 11 provided with a through hole suitable for housing said first screw 10.

The compression device 2 may obviously comprise any number of shaped washers 11, preferably at least three washers arranged circumferentially at fixed intervals, or four washers arranged at 90 degrees intervals, as shown in fig. 4.

According to a variant embodiment of the invention (not shown here), the reaction element 8 is a ring-like element, preferably but not necessarily connected to the thrust unit 7 by at least three screws arranged at regular intervals along the circumference.

The thrust unit 7 preferably comprises a support body 12 defining the above-mentioned reference surface 12a, the reference surface 12a being placeable against the locking ring 5.

As shown in fig. 2, it is evident that the maximum diameter of the above-mentioned support body 12 exceeds the internal diameter of the locking ring 5, so as to prevent the support body 12 from sliding off the tubular casing 3.

The thrust unit 7 also comprises a threaded element 13, the threaded element 13 being screwable on said support body 12 so that the threaded element 13 projects from the support body 12 from the side opposite to the reference surface 12 a.

Preferably, the threaded element 13 is a screw passing through a corresponding threaded hole provided in the support body 12.

Any number of screw elements 13 may be arranged at regular intervals along the circumference, but it is preferable to use three or more screw elements 13 as shown in fig. 4.

Preferably, but not necessarily, the thrust unit 7 comprises thrust bodies 14, against which the thrust bodies 14 can be placed when the threaded elements 13 are screwed onto the support body 12, and which are suitable to be arranged in contact on opposite sides with the stator unit 17.

The screwing of the threaded element 13 clearly causes the thrust body 14 to move away from the support body 12, so as to expand the thrust unit 7 and thus to propel the stator unit 17 and compress the stator unit 17.

Advantageously, the threaded element 13 enables the expansion of the thrust unit 7 to be adjusted in a simple manner.

Furthermore, the thrust body 14 is able to distribute the compression force exerted by the threaded element 13 over the entire circumference of the stator unit 17.

It is also evident that the thrust body 14 may be omitted, instead the threaded element 13 is arranged in direct contact with the stator unit 17 in order to compress the stator unit 17.

The threaded element 13 has a helical axis which is preferably inclined with respect to the expansion direction Y, as shown in fig. 2.

Advantageously, this brings the expansion force towards the outer diameter of the stator unit 17, wherein this marks its maximum stiffness.

Obviously, however, in a variant embodiment of the invention, the axis of the helix of the threaded element 13 may be parallel to the expansion direction Y.

Returning to fig. 3, it can be observed that the constraint means 4 comprise a stop surface 6 belonging to the inner surface 15 of the tubular casing 3, the stop surface 6 being substantially at right angles to the longitudinal axis X and preferably annular.

The above-mentioned stop surface 6 can be obtained, for example, by bending towards the inside of the metal sheet constituting the tubular housing 3.

The above-described bending operation advantageously makes it possible to obtain a stop surface 6 having a surface area greater than that obtainable, for example, by forming a groove in the thickness of the tubular housing 3.

Obviously, the stop surface 6 may be of a shape other than annular, for example a segment of a circle, if it is suitable to support the locking ring 5.

As shown in fig. 4, the locking ring 5 is preferably an open type elastic locking ring, the outer diameter of which is larger than the diameter of the inner edge of the above-mentioned stop surface 6 at rest, and the elastic ring 5 is elastically compressible so as to reduce the outer diameter thereof to be smaller than the above-mentioned inner diameter.

Preferably, the elastic locking ring 5 is substantially laminar in order to advantageously obtain a high elastic range and therefore enable the use of a stop surface 6 with a large surface area.

Furthermore, preferably, the locking ring 5 is made of stainless steel, so that it can advantageously resist the oxidizing action of the pumped liquid without releasing residues of the liquid itself, in particular when the liquid is water for human consumption.

In order to ensure that the elastic locking ring 5 is able to expand fully, even when it is deformed plastically, which is undesirable, for example, by incorrect assembly, it is preferable to use a reaction element 8 provided with a shaped surface 16, the shaped surface 16 being configured so as to be able to force the locking ring 5 to expand radially during the connection to the thrust unit 7, as shown in figure 3.

This can be obtained using a shaped washer 11 having an increasing cross section, for example in the shape of a truncated cone, in the direction opposite to the direction of connection to the thrust unit 7, so that it is arranged in contact with the inner diameter of the elastic locking ring 5 during the connection of the reaction element 8.

Preferably, the shaped washer 11 is provided, at one end of its truncated-cone-shaped portion, on the side opposite to the thrust unit 7, with a collar 11a suitable for abutting against the elastic locking ring 5.

Obviously, the above-described cross-section of the shaped washer 11 can also be used for the annular reaction element 8.

From an operational point of view, the pump 1 will be operated by following the following sequence: the stator unit 17, the thrust unit 7 and the locking ring 5 are inserted inside the tubular housing 3, assembled aligned along the direction of the longitudinal axis X.

Subsequently, the reaction element 8 is connected to the thrust unit 7 by tightening the screw 10, thus reinforcing the locking ring 5. Finally, the screw member 13 is tightened to compress the stator unit 17.

For the reasons stated above, it should be clear that the compression device described herein achieves the objects of the present invention.

In fact, the use of the reaction element 8 enables the locking ring to be reinforced and therefore to withstand higher compression forces on the stator than in the known art.

In practice, the device that is the subject of the invention may comprise other variants or modifications, even if these variants or modifications are not described here or shown in the figures, which must be considered protected by the present patent if they fall within the scope of the claims below.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the scope of protection of each element identified by way of example by such reference signs.

Claims (16)

1. A compression device (2) for a stator unit (17) of a compression pump (1), comprising:

a tubular housing (3), said tubular housing (3) defining a longitudinal axis (X) and being adapted to house said stator unit (17) in a predetermined assembly position;

a locking ring (5);

-constraining means (4), said constraining means (4) being adapted to constrain said locking ring (5) inside said tubular casing (3) in the direction of said longitudinal axis (X);

-a thrust unit (7), said thrust unit (7) being provided with a reference surface (12a) that can be placed against said locking ring (5), said thrust unit (7) being adapted to expand along an expansion direction (Y) perpendicular to said reference surface (12a), in such a way as to push one end of said stator unit (17) when arranged in said assembly position;

characterized in that said thrust compression device (2) comprises:

a reaction element (8), said reaction element (8) being placeable against said locking ring (5) on a side opposite to said thrust unit (7);

-connection means (9), said connection means (9) being intended to connect said reaction element (8) to said thrust unit (7), said connection means (9) being adapted to move said reaction element (8) towards said thrust unit (7) in order to arrange them against opposite sides of said locking ring (5).

2. A compression device (2) according to claim 1, wherein said connection means (9) comprises screw means (10, 10 a).

3. A compression device (2) according to claim 2, wherein said screw means (10, 10a) comprise a first screw (10), said first screw (10) being associated with said reaction element (8) and being adapted to be screwed into a nut (10a) belonging to said thrust unit (7).

4. A compression device (2) according to claim 3, wherein the first screw (10) is formed in one piece with the reaction element (8).

5. A compression device (2) according to any one of the preceding claims, wherein the reaction element (8) is a shaped washer (11).

6. A compression device (2) according to any one of claims 1 to 4, wherein the reaction element (8) is an annular body.

7. A compression device (2) according to claim 1, wherein the thrust unit (7) comprises a support body (12), the reference surface (12a) belonging to the support body (12), and a threaded element (13), the threaded element (13) being able to be screwed onto the support body (12) so as to protrude from the support body (12), from the side opposite to the reference surface (12 a).

8. A compression device (2) according to claim 7, wherein the threaded element (13) defines a helical axis, which is inclined with respect to the expansion direction (Y).

9. A compression device (2) according to claim 7 or 8, wherein the thrust unit (7) comprises a thrust body (14), the thrust body (14) being able to be placed against the threaded element (13) when the threaded element (13) is screwed onto the support body (12).

10. A compression device (2) according to claim 1, wherein said constraint means (4) comprise a stop surface (6), said stop surface (6) belonging to an inner surface (15) of said tubular casing (3), said stop surface (6) being substantially at right angles to said longitudinal axis (X).

11. A compression device (2) according to claim 10 wherein the locking ring (5) is a resilient ring, the outer diameter of the locking ring (5) at rest being greater than the inner diameter of the stop surface (6), and the locking ring (5) is resiliently compressible such that the outer diameter of the locking ring (5) is less than the inner diameter of the stop surface (6).

12. A compression device (2) according to claim 11 wherein the resilient locking ring (5) is laminated.

13. A compression device (2) according to claim 11 or 12, wherein the reaction element (8) comprises a shaped surface (16), the shaped surface (16) being configured to force the elastic locking ring (5) to expand when the reaction element (8) is connected to the thrust unit (7).

14. A compression device (2) according to claim 1, wherein the locking ring (5) is made of stainless steel.

15. The compression device (2) according to claim 1, wherein the stator unit (17) comprises a plurality of stacked stages (17 a).

16. Pump (1), the pump (1) comprising a compression device (2) according to any one of the preceding claims and a stator unit (17), the stator unit (17) being adapted to be inserted into the tubular casing (3) of the compression device (2) against the thrust unit (7).