Tightening member

1. A tightening member which is fitted around a first end of an elongated fixing means defining a longitudinal direction, and extending through an element to be joined, the tightening member comprising:

a first part which is fixed around the first end of the elongated fixing means in a manner which transmits tightening force, the first part having portions forming a front surface, which faces toward the second end of the elongated fixing means, and defining an outer diameter;

a second part, a portion of the second part forming a second front surface of the tightening member adapted for abutment to the element to be joined, the second part being placed around the first end of the elongated fixing means, separate from the elongated fixing means, and between the first part and the element to be joined;

a pressurized medium chamber formed between the first part and the second part;

a locking part effective between the first part and the second part, the locking part having an annular shape defining an inner surface and positioned around the first end of the elongated fixing means and positioned between the first part and the element to be joined, and lockably connected to the second part by said inner surface, and the locking part having a surface transverse to the longitudinal direction of the elongated fixing means, engageable when in a locking position, in abutment with the front surface of the first part;

wherein the second part has portions forming a first rearward surface facing toward the first end of the elongated fixing means, and having an outer wall defining an outer diameter and an inner wall defining an inner diameter, said first rearward surface of the second part being positioned in an annular recess formed in the first part, the recess having an inner wall, an outer wall, and a bottom, whereby the pressurized medium chamber is formed between said first rearward surface of the second part and the bottom of the recess; and

wherein the outer diameter of the second part is smaller than the outer diameter of the first part, and wherein the locking part is lockable to the second part, said second part having a butt end proximate said element to be joined, wherein the butt end narrows inwardly forming a recess in which the locking part is placed with the locking part inner surface in direct engagement with the second part.

2. The tightening member of claim 1 , wherein the first part is fixed by means of an inner thread to an outer thread at the first end of the elongated fixing means.

3. The tightening member of claim 2 , wherein the locking part has an outer surface which forms an extension in the longitudinal direction towards the element to be joined, to an outer surface of the first part which outer surface defines the outer diameter of the first part.

4. The tightening member of claim 3 wherein the annular recess forms part of the pressurized medium chamber and the inner thread extends in the longitudinal direction to an area adjacent the inner wall of the recess in the first part so that the inner wall cannot bend inwards in a radial direction when the inner thread engages the outer thread at the first end of the elongated fixing means.

5. The tightening member of claim 3 , wherein the inner surface of the locking part is threadedly engaged with the second part.

6. The tightening member of claim 2 wherein the annular recess forms part of the pressurized medium chamber and the inner thread extends in the longitudinal direction to an area adjacent the inner wall of the recess in the first part so that the inner wall cannot bend inwards in a radial direction when the inner thread engages the outer thread at the first end of the elongated fixing means.

7. The tightening member of claim 2 , wherein the pressurized medium chamber is sealed by means of a seal disposed between the outer wall of the annular recess and the outer wall of the second part, and by a seal disposed between the inner wall of the annular recess and the inner wall of the second part.

8. The tightening member of claim 2 , wherein the inner surface of the locking part is threadedly engaged with the second part.

9. The tightening member of claim 1 , wherein the first part is integral to the first end of the elongated fixing means.

10. The tightening member of claim 9 , wherein the pressurized medium chamber is sealed by means of a seal disposed between the outer wall of the annular recess and the outer wall of the second part, and by a seal disposed between the inner wall of the annular recess and the inner wall of the second part.

11. The tightening member of claim 1 , wherein the locking part has an outer surface which forms an extension in the longitudinal direction towards the element to be joined, to an outer surface of the first part which outer surface defines the outer diameter of the first part.

12. The tightening member of claim 1 , wherein the pressurized medium chamber is sealed by means of a seal disposed between the outer wall of the annular recess and the outer wall of the second part, and by a seal disposed between the inner wall of the annular recess and the inner wall of the second part.

13. The tightening member of claim 1 , wherein the inner surface of the locking part is threadedly engaged with the second part.

14. A hydraulic nut comprising:

a longitudinally extending fixing member, having a first end and a second end;

a first part connected around the first end of the longitudinally extending fixing member which can be rendered immobile with respect to the longitudinally extending fixing member, the first part having portions forming an annular recess which opens toward the second end of the longitudinally extending fixing member, the annular recess defining an inner wall, an outer wall, and a bottom wall which form the annular recess, the first part defining an outer diameter and a first surface between the outer wall of the annular recess and the outer diameter, said first surface facing the second end of the longitudinally extending fixing member;

a second part forming an annular member which has a portion which fits within the annular recess in the first part, the portion extending in a radial direction with respect to the longitudinally extending fixing member, between the inner wall and the outer wall of the annular recess, and wherein a pressurized medium chamber is defined between the portion and the annular recess, wherein the second part has an annular portion which extends longitudinally toward the second end of the longitudinally extending fixing member, and wherein said annular portion has an outer surface which is spaced radially inwardly of the outer wall of the annular recess, to form a locking part recess;

a locking part placed within the locking part recess, the locking part having an inner diameter which is threadedly engaged with the second part outer surface, the locking part having a surface facing the first part first surface, and movable by said threaded engagement with the second part to an abutment with the first part first surface.

15. The hydraulic nut of claim 14 wherein the first part is connected around the first end of the longitudinally extending fixing member, by being integral with the said longitudinally extending fixing member.

16. The hydraulic nut of claim 14 wherein the first part is threadedly connected around the first end of the longitudinally extending fixing member.

17. The hydraulic nut of claim 14 wherein the locking part does not extend radially beyond the first part.

18. The hydraulic nut of claim 14 wherein a threaded connection between the first part and the first end of the longitudinally extending fixing member extends in the longitudinal direction to an area adjacent the inner wall of the recess in the first part so that the inner wall cannot bend inwards in a radial direction.