Portable anti-skid device for tires of motor vehicles

The device according to the invention comprises a support body (11), in which a toothed pinion (12) is mounted able to rotate and in which a plurality of sliding crampons (14), essentially "L" shaped, are supported. Each crampon has a first branch (14.1) able to slide in a respective plane, substantially orthogonal to the axis of said pinion (12) and a second branch (14.2, 24.2), essentially orthogonal to the corresponding first branch. Each of said first branches of the crampons has a respective rack enmeshed with said pinion, so that when said pinion (12) is made to rotate in one or in the other sense, said first branches (14.1, 24.1) of the crampons (14, 24) are simultaneously driven to slide, in the respective guides (14.3, 24.3), arranging the crampons themselves alternatively either in the retracted position of minimum bulk, to take the device (10) out of service, or in extended working position, in which the device itself is mounted relative to a wheel provided with tyre (P).