CLAIMS
1. A guiding unit for slabs comprising at least two rolls (10, 10') connected to each
other along a common axis of rotation X,
wherein each roll (10, 10') comprises a first tubular element (12) and a second tubular element (5) external and coaxial to axis X and to the first tubular element (12) and removable from said first tubular element,
wherein each roll (10, 10') comprises a respective hub (1, 1') at its two ends,
wherein cooling channels (3, 30) are provided in each roll (10, 10') between said first tubular element (12) and said second tubular element (5) for the passage of a coolant liquid,
wherein said cooling channels (3, 30) are defined by grooves made on an outer surface of the first tubular element (12) and closed by an inner central surface of the second tubular element (5),
wherein each hub (1, 1') is provided with cavities communicating with the cooling channels (3, 30) 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 (10, 10'),
wherein a first hub (1) of each roll comprises a first inner chamber (13) for letting coolant liquid into the respective roll, from which diverge first inner ducts (14) communicating with a first outer annular channel (15) coaxial to the axis X and from which branch off second inner ducts (16) communicating with first ends of the cooling channels (3, 30) of the respective roll, and
wherein a second hub (1') of each roll comprises a second inner chamber (13') for letting coolant liquid out from the respective roll,
wherein third inner ducts (14') converge in said second inner chamber (13'), said third inner ducts (14') communicating with a second outer annular channel (15') coaxial to the axis X, and
wherein fourth inner ducts (16') arrive in said outer annular channel (15'), said fourth inner ducts (16') communicating with second ends of the cooling channels (3, 30) of said respective roll.
2. A guiding unit according to claim 1, wherein said second tubular element (5) 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, preferably by interference, on the respective hubs (1,1 ')■
3. A guiding unit according to claim 1 or 2, wherein the second hub (V) of a first roll (10) of said at least two rolls is arranged adjacent and specular to the first hub (1) of a second roll (10) of said at least two rolls, whereby the second inner chamber (13') of the second hub (V) of the first roll (10) communicates with the first inner chamber (13) of the first hub (1) of the second roll (10').
4. A guiding unit according to any one of the preceding claims, wherein the first annular channel (15) and the second annular channel (15) are defined by an annular groove made on an outer surface of the respective hub (1, 1') and closed by an inner end surface of a respective second tubular element (5), preferably said inner end surface defining an annular seat (20) for the respective hub.
5. A guiding unit according to any one of the preceding claims, wherein said cooling channels are defined by longitudinal grooves (3) parallel to axis X.
6. A guiding unit according to any one of the claims from 1 to 4, wherein said cooling channels are defined by helical grooves (30).
7. A guiding unit according to any one of the preceding claims, wherein said first tubular element (12) of each roll is a hollow cylinder fixed at the ends to the respective hubs (1, 1').
8. A guiding unit according to claim 2 or 7, wherein along axis X the longitudinal extension of the first tubular element (12) is substantially equal to the longitudinal extension of the second tubular element (5) minus the longitudinal extension of two annular end seats (20) for the hubs (1, 1'), delimited by a respective inner annular shoulder (21).
9. A guiding unit according to any one of the preceding claims, wherein bearings (6) are mounted exclusively on housings (2) obtained on each hub (1, 1').

10. A guiding unit according to claim 9, wherein there are provided sealing means (9) arranged between each bearing (6) and the corresponding second tubular element (5).
11. A guiding unit according to any one of the preceding claims, wherein the inlet sections and the outlet sections of the coolant liquid along said first annular

channel (15) and along said second annular channel (15') are appropriately mutually spaced part, preferably arranged in mutually alternating manner.