STATOR ELEMENT OF A PROGRESSIVE CAVITY PUMP AND PROGRESSIVE CAVITY PUMP

Abstract

Stator element of a progressive cavity pump and progressive cavity pump

The invention relates to a stator element of a progressive cavity pump. The stator element comprises: a reinforcement tube (20) having a longitudinal axis (A-A), an inner face (22), and an outer face (24), and an elastomer liner fixed to the inner face of the reinforcement tube, characterized in that at least a portion of the reinforcement tube (20) has a substantially constant thickness (e) and in that said portion of the reinforcement tube (20) is deformed such that it comprises at least a first relief pattern (28) and a second relief pattern (30), the first relief pattern (28) having the shape of a helical strip that is right-handed relative to the longitudinal axis (A-A), the second relief pattern (30) having the shape of a helical strip that is left-handed relative to the longitudinal axis (A-A), the first and second relief patterns meeting in at least one section (32).

Claims

1. Stator A stator element of a progressive cavity pump, said stator element comprising: a reinforcement tube having a longitudinal axis, an inner face and an outer face, and an elastomer liner fixed to the inner face of the reinforcement tube, wherein at least a portion of the reinforcement tube has a substantially constant thickness and said portion of the reinforcement tube is deformed such that it comprises at least a first relief pattern and a second relief pattern, the first relief pattern having the shape of a helical strip that is right-handed relative to the longitudinal axis of the reinforcement tube, the second relief pattern having the shape of a helical strip that is left-handed relative to the longitudinal axis of the reinforcement tube, the first relief pattern and the second relief pattern meeting in at least one section.

2. The stator element according to claim 1, wherein the first relief pattern and the second relief pattern meet in several sections, and wherein the intermediate areas located between the first relief pattern and the second relief pattern have the shape of a polygon of at least order 3.

3. The stator element according to claim 1, wherein the first relief pattern and the second relief pattern form grooves on the outer face of the portion of the reinforcement tube.

4. The stator element according to claim 1, wherein the elastomer liner has an outer face fixed to the inner face of the reinforcement tube and an inner face of helical shape having a pitch, and wherein the pitch of the helical strip of the first relief pattern is identical to the pitch of the helical shape of the inner face of the elastomer liner.

5. The stator element according to claim 1, wherein the reinforcement tube comprises a cylindrical portion at each end and wherein said stator element comprises at least one axial retaining ring fixed to the cylindrical portion of the stator element, said retaining ring having a radial cross-section of a general U-shape suitable for surrounding a portion of a longitudinal end of the elastomer liner.

6. The stator element according to claim 5, wherein at least one inner face of an axial arm of the retaining ring has sawtooth-shaped protrusions.

7. A progressive cavity pump comprising: a helical rotor rotatably mounted in the elastomer liner, at least first and second stator elements according to claim 5, and a tubular section fitted, on one side, into said cylindrical portion of the first stator element, and on the other side, into said cylindrical portion of the second stator element, said tubular section bearing, on one side, against the retaining ring of the first stator element, and on the other side, against the retaining ring of the second stator element, said tubular section forming a stop suitable for preventing axial displacement of the retaining rings.

8. The progressive cavity pump according to claim 7, further comprising a tubular end piece having a threaded portion and an opposite portion fitted into another cylindrical portion of the second stator element, said tubular end piece forming a stop preventing axial displacement of the retaining ring.

9. The progressive cavity pump according to claim 7, wherein the cylindrical portion of the first stator element, the cylindrical portion of the second stator element, and the tubular section are fixed by welding.

10. The progressive cavity pump according to claim 8, wherein the cylindrical portion of the second stator element and the tubular end piece are fixed by welding.

Description

[0028] The invention will be better understood by reading the following description, given solely as an example and with reference to the figures in which:

[0029] FIG. 1 is an exploded side view of a progressive cavity pump;

[0030] FIG. 2 is a longitudinal section view of a stator element according to a first embodiment of the invention;

[0031] FIG. 3 is a perspective view of a portion of a reinforcement tube of the stator element illustrated in FIG. 2;

[0032] FIG. 4 is a longitudinal section view of the portion of reinforcement tube illustrated in FIG. 3;

[0033] FIG. 5 is a longitudinal section view of a portion of two stator elements according to a second embodiment of the invention, the two stator elements being partially assembled;

[0034] FIG. 6 is a cross-sectional view of the stator element illustrated in FIG. 5, along section plane VI-VI; and

[0035] FIG. 7 is a longitudinal section view of an assembly of a portion of a stator element according to the second embodiment and a tubular end piece.

[0036] The invention relates to a stator element and a progressive cavity pump which can be used as a pump or as a drilling motor.

[0037] With reference to FIG. 1, the progressive cavity pump 2 according to a first embodiment of the invention comprises a first 4, a second 6, and a third 8 stator elements, two tubular sections 10, 12, two tubular end pieces 14, 16, and a helical rotor 18 rotatably mounted in the stator elements, the tubular sections, and the tubular end pieces.

[0038] Each tubular section 10, 12 is fitted between two stator elements 4, 6 and 6, 8, and makes it possible to fix the stator elements to one another and to center them relative to one another. The tubular end pieces 14, 16 are fitted into the free ends of the first 4 and third 8 stator elements. They comprise a threaded portion 13 enabling the attachment of the pump 2 to another pump or to a housing of a pumping facility.

[0039] The first 4, second 6, and third 8 stator elements are identical. They may be implemented according to a first embodiment illustrated in FIGS. 2 to 4 or according to a second embodiment illustrated in FIGS. 5 to 7.

[0040] Referring to FIG. 2, the first stator element 4 according to the first embodiment comprises a reinforcement tube 20 extending along a longitudinal axis A-A, and an elastomer liner 26 fixed in the reinforcement tube.

[0041] The reinforcement tube 20 comprises a deformed central portion 21 and, at each of its ends, a cylindrical portion 23 with a circular base. It has an inner face 22 and an outer face 24.

[0042] The elastomer liner 26 has an outer face 40 fixed to the inner face 22 of the reinforcement tube, and an inner face 42 of helical shape having a pitch p1.

[0043] Referring to FIGS. 3 and 4, the central portion 21 of the reinforcement tube 20 has a substantially constant thickness e and is deformed such that it comprises a first relief pattern 28 and a second relief pattern 30. The relief patterns 28, 30 may be raised or recessed. They are for example obtained by knurling the inner face 22 or outer face 24 of the central portion of the reinforcement tube. The first 28 and second 30 relief patterns form, on the inner face of the central portion of the reinforcement tube, gripping members for the elastomer liner 26. These gripping members prevent the liner from being pulled off.

[0044] In particular, according to the invention the first relief pattern 28 has the shape of a helical strip that is right-handed relative to the longitudinal axis A-A of the reinforcement tube. The second relief pattern 30 is in the form of a helical strip that is left-handed relative to the longitudinal axis A-A of the reinforcement tube. Due to this helical shape and the fact that the handedness of the helical strips are opposite, the first 28 and second 30 relief patterns prevent the elastomer liner from being pulled off regardless of the direction of the forces applied to it. Thus, the integral attachment between the inner face 22 of the reinforcement tube and the outer face 40 of the elastomer liner better withstands the axial and orthoradial forces generated during rotation of the helical rotor 18.

[0045] According to the preferred embodiment of the invention illustrated in FIGS. 3 and 4, the relief patterns 28, 30 are formed by recesses on the outer face 24 of the reinforcement tube. These recesses are called helical grooves 34 below. In this example, these helical grooves 34 are produced by knurling the outer face 24 of the reinforcement tube. These helical grooves 34 form helical indentations 36 on the inner face 22 of the reinforcement tube.

[0046] The first 28 and second 30 relief patterns meet in several sections 32. Intermediate areas 38 located between the first relief pattern 28 and the second relief pattern 30 have a concavity opposite to the concavity of the first 28 and second 30 relief patterns. Thus, in the embodiment illustrated in FIGS. 3 and 4, the areas 38 form protrusions on the outer face 24 of the reinforcement tube. In this embodiment, these intermediate areas 38 have the shape of a polygon of order 4.

[0047] Advantageously, the pitch p2 of the helicoid of the first relief pattern 28 is identical to the pitch p1 of the helicoid of the inner face 42 of the elastomer liner.

[0048] The second and third stator elements according to the first embodiment are identical to the first stator element and will not be described in detail.

[0049] Alternatively, the relief patterns are constituted by projections which extend outwardly from the anchoring tube and which form recesses on the inner face of the reinforcement tube 20.

[0050] Alternatively, the reinforcement tube 20 is deformed such that it comprises a number of relief patterns that is greater than two.

[0051] Alternatively, the pitch of the helicoid of the first relief pattern 28 and the pitch of the helicoid of the second relief pattern 30 is substantially greater than or equal to the length of the reinforcement tube 20 such that the first relief pattern 28 and second relief pattern 30 meet in a single section 32.

[0052] Alternatively, the areas 38 positioned between the first strip and second strip have the shape of a polygon of order 3.

[0053] FIGS. 5 to 7 represent stator elements according to a second embodiment of the invention. In particular, FIG. 5 represents a first 4 and a second 6 stator element which are partially assembled to the tubular section 10.

[0054] The first, second, and third stator elements according to the second embodiment of the invention are similar to the first, second, and third stator elements according to the first embodiment except for the existence of two retaining rings 44 fixed in each stator element.

[0055] The parts of the stator elements according to the second embodiment which are identical to the parts of the stator elements according to the first embodiment have the same references and will not be described a second time.

[0056] With reference to FIGS. 5 and 6, the retaining rings 44 of the first 4 and second 6 stator elements are able to delay infiltration of the fluid pumped between the reinforcement tube 20 and the elastomer liner 26. They retain the longitudinal ends of the elastomer liner 26 against the inner face 22 of the reinforcement tube.

[0057] The retaining rings 44 are fixed in each cylindrical portion 23 of the reinforcement tube 20, coaxially with the longitudinal axis A-A. In practice, the elastomer liner 26 is shaped by injecting an uncured elastomer mixture into the reinforcement tube 20 when the latter is equipped with two retaining rings 44.

[0058] The retaining rings 44 have a U-shaped cross-section suitable for surrounding a portion of the longitudinal end of the elastomer liner 26. The U-shaped radial cross-section of the retaining rings comprises an outer axial arm 46, a central radial arm 48, and an inner axial arm 50.

[0059] The outer axial arm 46 is fixed to the inner face 22 of the cylindrical portion 23 of the reinforcement tube. The central radial arm 48 forms an axial stop for the tubular section 10 during assembly of the first 4 and second 6 stator elements.

[0060] An inner face 52 of the inner axial arm 50 comprises sawtooth-shaped protuberances 54 suitable for retaining the elastomer of the liner 26.

[0061] The retaining rings 44 form stops preventing axial displacement of the elastomer liner 26 and thus delay its pulling loose.

[0062] When the first stator element 4, the tubular section 10, and the second stator element 6 are assembled and secured together by applying a welding material at the chamfers 56, the tubular section 10 in turn forms a stop preventing axial displacement of the retaining ring 44 of the first stator element and of the retaining ring 44 of the second stator element.

[0063] With reference to FIG. 7, the third stator element 8 is fixed to the tubular end piece 16 by a weld 57. The tubular end piece 16 has a threaded portion 13 and an opposite portion 58 fitted into the cylindrical portion 23 of the second stator element 6. As can be seen in this figure, the retaining ring 44 bears against the tubular end piece 16. When the tubular end piece 16 is welded to the third stator element, the tubular end piece 16 forms a stop preventing axial displacement of the retaining ring 44.