WE CLAIM
1. A rolling stand (100), defining a rolling axis, comprising
a support structure (13),
a roll holder cartridge (3) configured to go from a working position inside the support structure (13), at said rolling axis, to an extracted position outside the support structure (13) with a transverse movement with respect to the rolling axis, three rolling rolls (2, 2', 2"), each of which having a respective yoke support (6, 6', 6"), arranged in the roll holder cartridge (3) with axes thereof arranged at 120o with respect to one another, a first roll (2) of said three rolling rolls having rotation axis thereof arranged vertically,
at least one hydraulic capsule (4, 4', 4") for each rolling roll (2, 2', 2") fixed to the support structure (13), for adjusting the radial position of the respective rolling roll, the hydraulic capsule having a respective thrust cylinder and being configured to allow the respective thrust cylinder to cover a distancing stroke from the rolling axis sufficient to allow to clear the path of the roll holder cartridge (3) between the working position and the extracted position, wherein the roll holder cartridge (3) has a longitudinal open slot (10), the central axis of which coincides with the longitudinal central axis of the yoke support (6) of the first roll (2), and a width in vertical direction greater than the diameter of the tube being rolled, said open slot (10) being closed at a first end near the rolling axis and open at a second end opposite to the first end and coinciding with a side of the roll holder cartridge (3), considering the position assumed by the roll holder cartridge (3) when it is inserted in the rolling stand.
2. The rolling stand (100) as claimed in claim 1, comprising a locking device (7, 8, 9) of the position of the yoke supports (6, 6', 6") inside the roll holder cartridge (3).
3. The rolling stand as claimed in claim 1, wherein the hydraulic capsules (4, 4', 4') are four-way capsules.
4. The rolling stand (100) as claimed in claim 1, comprising a balancing device of the yoke support (6) of the vertical axis roll (2) that is coaxial with the piston of the corresponding hydraulic capsule (4) and provided with a hammer head that is retractable and rotational with respect to the axis thereof.
5. The rolling stand (100) as claimed in claim 1, wherein a V-shaped seat is arranged on the fixed structure formed by two supporting planes (14, 14") inclined with respect to the
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horizontal axis and aligned with the guides of the yoke support (6) for centering and supporting the yoke support (6) of the vertical axis roll (2) when it is withheld by the corresponding hydraulic capsule (4).
6. A method for releasing a rolling stand (100) as claimed in claim 1 in case of sticking of a tube during rolling operations, said method comprising in sequence the following steps of:
a) releasing the retainer (8) between yoke support (6) of the vertical axis roll (2) and the roll holder cartridge (3),
b) releasing the extensions (5, 5', 5"),
c) shifting the roll holder cartridge (3) laterally from the working position to the extraction position,
d) retracting the piston of the horizontal axis hydraulic capsule (4) so as to move the inclined planes (14", 14"') of the corresponding yoke support (6) into contact with reaction surfaces (14, 14') integral with the support structure of the rolling stand,
e) maintaining the balancing force during the entire time needed to avoid the sliding of the yoke support (6) of the vertical axis roll (2) on the inclined planes (14, 14') or the tipping thereof due to the unbalanced weight,
f) extracting the roll holder cartridge (3) leaving the yoke support (6) with the related vertical
axis roll (2) on the support structure of the rolling stand.