Device for the automatic demounting of a tire from a rim and machine equipped with such device

The present invention relates to a device for the automatic demounting of a tire from a rim having: - a support arm (4) being liftable and lowerable in a direction substantially parallel to the rotation axis (x-x), - a demounting tool (10) articulated to the support arm (4), - an attachment member (12) for the demounting tool (10), comprising a first and a second articulation pin (13,14) extending substantially parallel to each other, - at least one extension appendage of the support arm (4) or a section (17) of the support arm (4), which extends beyond the second articulation pin (14), and - at least one tie rod member (18) that is articulated on one side to the tool, and on the other side to the extension appendage or section (17) of the support arm (4).