Pattern drum with pattern size increasing apparatus

A circular knitting machine for manufacturing knitted fabrics having a pattern thereon, comprising a needle cylinder having longitudinal grooves and needles and selector jacks slidable within a number of said grooves, thereby difining a needle fitted out portion of said needle cylinder and a needle free portion thereof, said selector jacks being grouped in groups around the needle cylinder and each having a butt, the butts of adjacent selector jacks of each group being arranged at different heights, at least one pattern drum disposed peripherally with respect to said needle cylinder and provided with a plurality of pattern teeth for engagement with said butts to cause selection of the needles according to the pattern to be reproduced on the fabric, said at least one pattern drum having said pattern teeth disposed along vertical lines spaced by an extent equal to the distance between two adjacent needles of said needle cylinder, a support structure rotatably arranged around said needle cylinder and rotatably supporting said at least one pattern drum, means for rotating said support sturcture, means for causing said at least one pattern drum to revolve relative to said needle clinder during rotation of said support structure around said needle cylinder, means at said needle free portion of said needle cylinder for partially rotating said at least one pattern drum relative to said needle cylinder after a relative revolution of said at least one pattern drum about the circumferential extent of said needle fitted out portion of said needle cylinder so as to cause a given pattern tooth of said at least one pattern drum engaging a selector jack at a given time to become phase displaced with respect to said selector jack by an extent at least once the distance between two adjacent needles after a complete relative revolution of said at least one pattern drum about the whole circumferential extent of said needle cylinder, and means for resetting said at least one pattern drum and said needle cylinder in the condition in which said given selector jack newly engages said pattern tooth after a determined number of relative revolutions of said at least one pattern drum about said needle cylinder.