Guiding unit for slabs in a continuous casting plant

1. A guiding unit for slabs comprising at least two rolls connected to each other along a common axis of rotation X,

wherein each roll comprises a first tubular element and a second tubular element external and coaxial to the common axis X and to the first tubular element and removable from said first tubular element,

wherein each roll comprises a respective hub at its two ends,

wherein cooling channels are provided in each roll between said first tubular element and said second tubular element for a passage of a coolant liquid,

wherein said cooling channels are defined by grooves made on an outer surface of the first tubular element and closed by an inner central surface of the second tubular element,

wherein each hub is provided with cavities communicating with the cooling channels of the respective roll so as to define a path for the coolant liquid from a first end to a second end of the guiding unit, the path crossing said at least two rolls,

wherein a first hub of each roll comprises a first inner chamber for letting coolant liquid into the respective roll, from which diverge first inner ducts communicating with a first outer annular channel coaxial to the common axis X and from which branch off second inner ducts communicating with first ends of the cooling channels of the respective roll, and

wherein a second hub of each roll comprises a second inner chamber for letting coolant liquid out from the respective roll,

wherein third inner ducts converge in said second inner chamber, said third inner ducts communicating with a second outer annular channel coaxial to the common axis X, and

wherein fourth inner ducts arrive in said outer annular channel, said fourth inner ducts communicating with second ends of the cooling channels of said respective roll.

2. The guiding unit according to claim 1 , wherein said second tubular element is a cylindrical sleeve provided with an annular inner shoulder at its ends and with an annular end seat delimited by said annular inner shoulder for fitting on the respective hubs.

3. The guiding unit according to claim 2 , wherein along the common axis X a longitudinal extension of the first tubular element is substantially equal to a longitudinal extension of the second tubular element minus a longitudinal extension of two annular end seats for the hubs, delimited by a respective inner annular shoulder.

4. The guiding unit according to claim 2 , wherein said cylindrical sleeve is provided with an annular inner shoulder at its ends and with an annular end seat delimited by said annular inner shoulder for fitting by interference on the respective hubs.

5. The guiding unit according to claim 1 , wherein the second hub of a first roll of said at least two rolls is arranged adjacent and specular to the first hub of a second roll of said at least two rolls, whereby the second inner chamber of the second hub of the first roll communicates with the first inner chamber of the first hub of the second roll.

6. The guiding unit according to claim 1 , wherein the first outer annular channel and the second outer annular channel are defined by an annular groove made on an outer surface of the respective hub and closed by an inner end surface of a respective second tubular element.

7. The guiding unit according to claim 6 , wherein said inner end surface defines an annular seat for the respective hub.

8. The guiding unit according to claim 1 , wherein said cooling channels are defined by longitudinal grooves parallel to the common axis X.

9. The guiding unit according to claim 1 , wherein said cooling channels are defined by helical grooves.

10. The guiding unit according to claim 1 , wherein said first tubular element of each roll is a hollow cylinder fixed at its ends to the respective hubs.

11. The guiding, unit according to claim 10 , wherein along the common axis X a longitudinal extension of the first tubular element is substantially equal to a longitudinal extension of the second tubular element minus a longitudinal extension of two annular end seats for the hubs, delimited by a respective inner annular shoulder.

12. The guiding unit according to claim 1 , wherein bearings are mounted exclusively on housings obtained on each hub.

13. The guiding unit according to claim 12 , wherein there are provided sealing means arranged between each bearing and the corresponding second tubular element.

14. The guiding unit according to claim 1 , wherein inlet sections and outlet sections of the coolant liquid along said first outer annular channel and along said second outer annular channel are appropriately mutually spaced part.

15. The guiding unit according to claim 14 , wherein the inlet sections and the outlet sections of the coolant liquid along said first outer annular channel and along said second outer annular channel are arranged in mutually alternating manner.