Safety binding heelpiece for skis

Heel unit (10) of a safety ski binding, comprising a base body (14) intended to be fixed to a ski (12), a return cam (26) rotatably mounted on the base body (14) about an axis (A) and returned by a first spring device (28) into a rotary starting position, a sole holder (16) rotatably mounted about the axis (A), a unidirectional blocking arrangement (60) arranged between the return cam (26) and the sole holder (16) comprising at least one blocking arrangement (60), said blocking arrangement including at least one blocking member for blocking said sole holder in an opening direction of the sole holder and said blocking member being releasable against the slight spring force of a second spring device (66) by means of a manual release lever (64), one of the return cam (26) and the sole holder (16) being provided with a bearing face (68), having a generally circular shape and being concentric to the axis (A) of the return cam and of the sole holder, for the blocking member (62) which is permanently resiliently urged into a blocking position between the return cam (26) and the sole holder (16), said blocking member (62) being supported in a force-locked manner on the bearing face (68) when the sole holder is urged in the opening direction, and permanently engaging the bearing face (68) without force transfer when the sole holder is urged in a closing direction, substantially independently of the actual rotary position of the sole holder (16) relative to the return cam (26), to permit a relative displacement of the sole holder (16) with respect to the return cam (26) in the closing direction and substantially without effort.