Closure device particularly for ski boots

A closure device particularly for ski boots, comprising a box-like body fixable to a boot portion, a spool rotatably arranged within said box-like body, at least one cable having one end secured to said spool for being wound thereon and unwound therefrom, said at least one cable engaging another boot portion outwardly of said box-like body for selectively tightening and loosening said another boot portion with respect to said boot portion, a knob externally of said box-like body and rotatable with respect thereto for operation of said spool, ratchet means for locking said spool upon rotation of said knob in one direction and releasing said spool upon rotation of said knob in an opposite direction, said ratchet means comprising a ratchet member having a ratchet serration and a sleeve portion rigid therewith and coaxial with said knob, and a pawl selectively engageable with, and disengageable from, said ratchet serration, wherein said ratchet member is axially undisplaceable with respect to said spool but rotatively connected therewith and has a thread formation on said sleeve portion, and wherein said knob has a threading matching with said thread formation on said sleeve portion and a projection for operation of said pawl, said knob being threadable on said sleeve portion into a position rigid with said ratchet member for rotation of said spool in a cable winding direction, and unthreadable on said sleeve portion into a position in which said projection disengages said pawl from said ratchet serration and said knob is rigid with said ratchet member for rotation of said knob in said opposite direction to cause unwinding of said at least one cable from said spool.