Mounting and dismounting mechanism for a straightening or calibrating roller rotatable about a spindle and provided with a circular groove

A mounting and dismounting mechanism for a straightening or calibrating roller having a circular groove, the mechanism comprising a spindle, the spindle having a largest diameter portion, a large diameter portion, a reduced diameter spindle extension and a collar formed between the largest diameter portion and the large diameter portion, the roller being adapted to be mountable and clampable around the spindle to abut against said collar, and to be dismountable and removable from around the spindle co-directionally with a longitudinal axis (A) of the spindle and, the reduced diameter spindle extension providing the roller a preliminary alignment and for guiding the roller smoothly around the spindle, the spindle having a wall with an outer surface and a cylindrical cavity, the wall provided with at least one opening, at least one holder element being adapted to move within the cylindrical cavity between clamping and release positions thereof, respectively protruding through the at least one opening to protrude from the outer surface of the spindle to retain a roller to the spindle and not protruding from the outer surface of the spindle, a pusher adapted to be movably located within the cylindrical cavity and being movable between clamping and release positions thereof, the pusher being formed with a thrust face to engage the holder element, and a biasing means biasing the pusher to shift from its release position to its clamping position whereby the thrust face of the pusher moves the at least one holder element from its release position to its clamping position protruding from the outer surface of the spindle to retain a roller to the spindle, and a plunger affixed to the pusher, whereby the pusher is movable against the force of the biasing means from its clamping position to its release position, the at least one holder element being thus capable of shifting from its clamping position to its release position wherein the roller can be removed from said mechanism without removing any components from said mechanism.