Thread-tension regulating device for multi-thread sewing machine

A thread-tension regulating device of a multi-thread sewing machine comprising:

• a plurality of operating rods reciprocable in a longitudinal direction thereof;
• pairs of tension discs mounted on the respective operating rods;
• biasing means for elastically urging each pair of the tension discs toward each other and imparting tension varying in accordance with the reciprocating movement of the corresponding operating rod to a thread passing between the paired tension discs and thereafter supplied to a multi-thread sewing machine;
• a cam shaft extending perpendicularly to said plurality of operating rods;
• a plurality of cams fixedly mounted on said cam shaft, each of said cams having a peripheral surface engaging one end of each of said plurality of operating rods respectively;
• and
• infinite speed variator means comprising a first friction wheel for rotating said cam shaft, a second friction wheel disposed separately but concentrically with said first friction wheel and having the same diameter as that of the first friction wheel, a wheel shaft disposed perpendicular to the common axis of the first and second friction wheels, third and fourth friction wheels mounted on the respective ends of said wheel shaft and having inner surfaces in contact with the peripheral surfaces of the first and second friction wheels;
• and moving means for moving said third and fourth friction wheels substantially along the common axis of the first and second friction wheels.