Double-cylinder circular hosiery knitting machine with device for tensioning the manufacture

A double-cylinder circular hosiery knitting machine, comprising a supporting structure which is provided with a footing for resting on supports, so as to allow rotation about a vertically oriented axis, a lower needle cylinder and an upper needle cylinder located, during the production of a product, above and coaxially with respect to said lower needle cylinder;

• said lower needle cylinder and said upper needle cylinder being actuatable with a rotary motion about the respective axes;
• a device for tensioning the product during its production being accommodated inside said needle cylinders;
• said device for tensioning the product comprising means for retaining the product proximate to the region where knitting is formed by needles accommodated in said needle cylinders and a tensioning tube, which is accommodated in said upper needle cylinder and is movable on command along an axis of said upper needle cylinder;
• a lower end of said tensioning tube being engageable, by sliding along the axis of said upper needle cylinder, with the product being formed that lies from said retention means to the needles;
• said retention means having a size suitable to allow the movement of said tensioning tube about said retention means, means for the translational motion of said tensioning tube along the axis of said upper needle cylinder being provided, wherein said retention means comprise a suction tube, which is accommodated internally and coaxially to said lower needle cylinder, and an element for locking the product, which faces an upper end of said suction tube and is supported by said upper needle cylinder, said locking element being movable on command along the axis of said upper needle cylinder to engage or disengage the upper end of said suction tube.