Circular knitting machine and a method for moving the needles of a circular knitting machine

A circular knitting machine, comprising:

• a needle-holding cylinder having a plurality of longitudinal grooves arranged around a central axis of the needle-holding cylinder;
• a plurality of needles, each being housed in a respective longitudinal groove;
• actuating cams arranged around the needle-holding cylinder and movable with respect to said needle-holding cylinder around the central axis for causing or allowing movement of the needles along the longitudinal grooves so as to enable stitch formation by said needles;
• a drive chain for each needle inserted into the respective longitudinal groove, located below the needle and operatively placed between the needle and said actuating cams;
• wherein said drive chain comprises:
• a sub-needle slidingly arranged in the respective longitudinal groove below the needle and having a butt, wherein the butt is radially movable between an operating position, in which it is extracted so as to engage with respective first paths defined by first actuating cams and cause activation of the needle and stitch formation by the needle, and a non-operating position, in which it is retracted so as not to engage with said first paths;
• a selector at least partly slidingly arranged in the respective longitudinal groove below the sub-needle, having at least one respective butt radially movable between an operating position, in which it is extracted so as to engage with respective second paths defined by second actuating cams, and a non-operating position, in which it is retracted so as not to engage with said second paths;
• at least one selecting device acting under control upon said selector for switching the latter into or retaining it in the operating position or the non-operating position;
• a punch slidingly arranged in the respective longitudinal groove between the sub-needle and the selector, wherein a lower portion of the punch is engaged with the selector and an upper portion of the punch is engaged with the sub-needle, wherein the punch has a respective butt which can be engaged with respective third paths defined by third actuating cams;
• wherein the drive chain comprises an activating element slidingly arranged in the respective longitudinal groove between the sub-needle and the selector, wherein the activating element can be longitudinally moved with respect to the punch and with respect to the sub-needle and can be operatively engaged with the sub-needle so as to switch the butt of the sub-needle into and retain it in the respective operating position.