Circular knitting machine, particularly for producing items of clothing with three-dimensional shapes

A circular knitting machine, comprising:

• a footing, a needle cylinder supported on said footing so as to be rotatable about an axis thereof, which is orientated substantially vertically, said needle cylinder having a diameter that is substantially comprised between 7 and 24 inches, and multiple axial slots that are formed on an outer lateral surface thereof, needles each of which is accommodated in a corresponding slot;
• actuation means for actuating the needles which interact with said needles during rotation of the needle cylinder about said axis for actuation of the needles along the corresponding axial slot of the needle cylinder so that the needles form knitting with at least one yarn dispensed to the needles at least one drop or feed of the machine;
• and wherein said needle cylinder is rotationally actuatable about said axis in both directions of rotation and wherein said needle actuation means are adapted to allow the needles to form knitting in both directions of rotation of the needle cylinder about said axis at at least one drop or feed of the machine, wherein said needle cylinder is actuatable with an alternating rotary motion about said axis and wherein said needle actuation means comprise, for each needle, a sub-needle arranged in the corresponding axial slot of the needle cylinder below a corresponding needle;
• sub-needle actuation cams;
• said sub-needle being connected bilaterally to the corresponding needle for motion along the corresponding axial slot and having, along an extension thereof, a sub-needle heel that is orientated radially with respect to the needle cylinder, said sub-needle being able to oscillate on a radial plane of the needle cylinder in order to pass from an active position, in which the sub-needle is extracted radially with said sub-needle heel from the corresponding axial slot of the needle cylinder so as to engage paths formed by the sub-needle actuation cams, which are arranged around the needle cylinder and are adapted to produce or allow a movement of said sub-needle along the corresponding axial slot of the needle cylinder, to an inactive position, in which the sub-needle is embedded with its heel in the corresponding slot of the needle cylinder so as to avoid engaging said sub-needle actuation cams;
• and further actuation means which act on said sub-needle for transition thereof from said active position to said inactive position and vice versa.