Insulated capping head

A capping head (11) for applying caps (CC) onto containers (RR), said capping head generally comprising a substantially vertically extending support structure (13), in which a lower base (15) and an upper base (17) are defined connected to each other by a vertical slide guide, a mouth presser (16) having a vertical axis and being rotatably associated with the lower base (15) of the capping head (11) for exerting a predetermined pressure onto a cap (CC) fitted on the mouth of a container (RR) located under the mouth presser (16), and at least one pivoting arm (27) which is provided with a threading roller or knurling roller (29), is hinged to the support structure (13) and can take a rest configuration, in which the roller (29) is distal to the vertical axis of the mouth presser (16), and a working configuration, in which the roller (29) is proximal to said vertical axis, characterized in that it comprises a drive cam (25) for driving the pivoting motion of the arm (27), said drive cam (25) being slidable relative to the slide guide between a position corresponding to the rest configuration of the arm (27) and a position corresponding to a working configuration of the arm (27), and a central housing (31), which extends axially inside the structure and is provided with at least one deformable portion and in which a chamber (31a) insulated from the outer environment is defined, said chamber housing a movable member (37) capable of imparting the sliding motion to said cam (25) located outside said central housing (31).