Stator element of a progressive cavity pump and progressive cavity pump

1. 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 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 a 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 axial 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 axial 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 axial retaining ring of the first stator element, and on the other side, against the axial retaining ring of the second stator element, said tubular section forming a stop suitable for preventing axial displacement of the axial 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 axial retaining ring.

9. 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.

10. 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.