Self-adjusting drum system

1. A self-adjusting drum system for use with a pump, comprising:

a balancing drum mounted on a central shaft for joint rotation therewith, said shaft extending along an axial direction, said balancing drum having an outer surface thereof;

a fixed, stationary structure surrounding said balancing drum, said stationary structure having an inner surface arranged so as to face said outer surface of the balancing drum with an annular gap being provided therebetween;

a bush element arranged in said annular gap so as to leave a clearance with respect to said inner surface or said outer surface; and

fixing means for fixing said bush element to said stationary structure so as to lock the bush element against rotation movement and movement along the axial direction and allow the bush element to freely move along a radial direction, inside said annular gap.

2. The self-adjusting drum system according to claim 1 , wherein said fixing means comprise:

a pin;

a radial slot provided in said stationary structure and having an extension along said radial direction that is greater than a diameter of said pin; and

a locking element;

said pin having an end portion and being arrangeable at an end of said bush element with said end portion protruding therefrom, said end portion being accommodateable inside said radial slot and free to move thereinside in the radial direction, and

said locking element being suitable to lock said bush element to said stationary structure,

whereby said pin and locking element are suitable to prevent the rotation movement and the movement of said bush element along said axial direction but not along said radial direction.

3. The self-adjusting drum system according to claim 1 , wherein said fixing means comprise:

a pin having a pin end portion;

an axial recess provided in said bush element so as to face said inner surface of the stationary structure and having a depth extension along said radial direction up to a bottom part thereof; and

a locking element;

said pin being inserted radially through said stationary structure to protrude with said pin end portion thereof in said axial recess, towards said bottom part, so as to allow movement of said bush element in said radial direction; and

said locking element being suitable to lock said bush element to said stationary structure,

whereby said pin and said locking element are suitable to prevent the rotation movement and the movement of said bush element along said axial direction but not along said radial direction.

4. The self-adjusting drum system according to claim 2 , wherein radial extension of said radial slot is set so as to allow a movement of said end portion of the pin thereinside, along the radial direction, that is at least equal to said clearance.

5. The self-adjusting drum system according to claim 3 , wherein said depth extension of the axial recess is bigger than said clearance.

6. The self-adjusting drum system according to claim 3 , wherein said pin end portion protrudes in said axial recess up to a distance from said bottom part that is at least equal to said clearance.

7. The self-adjusting drum system according to claim 3 , wherein said pin is provided so as to allow said pin end portion to resiliently move in said radial direction following to a pushing action of said bottom region of the axial recess thereagainst, whereby to allow corresponding radial movement of said bush element.

8. The self-adjusting drum system according to claim 1 , wherein said bush element has, at a first end thereof, a lip portion that protrudes radially therefrom so as to abut on a shoulder of said stationary structure.

9. The self-adjusting drum system according to claim 8 , wherein said locking element is mounted at a second end of said bush element.

10. The self-adjusting drum system according to claim 8 , further comprising a sealing element suitable to seal said lip portion to said shoulder of said stationary structure so as to prevent fluid leakage from said annular gap.

11. The self-adjusting drum system according to claim 1 , wherein said balancing drum has a plurality of annular channels indenting said outer surface thereof so as to be in communication with said annular gap.

12. A pump comprising the self-adjusting drum system according to claim 1 , wherein the central shaft supports thereon an impeller of the pump, and the stationary structure is a casing or part of a casing of the pump.

13. The pump according to claim 12 , wherein when pressurized fluid is flowed inside the annular gap formed between the outer surface of the balancing drum and the inner surface of the stationary structure, the bush element arranges itself in a hydrostatically centered position inside said annular gap by way of radial movement along said radial direction, so as to provide, during pump operation, minimum clearance sufficient for free rotation of the drum.