above from the opening meanwhile the driving shaft 10 rotates the first gear 12 which in turn rotates the second gear 14 which causes the first link 18 to rotate together with the rotating disc 20 hence the rod 22 starts a reciprocating motion with a center in its upper part further the revolving roller 24 disposed in the cam groove 21 formed in the rotating disc 20 is also rotated by action of the rotation of the rotating disc 20 hence the crank 26 is moved vertically then the connector 30 is moved by the vertical motion of the crank 26 this time the connector 30 is moved from back to front from left to right with reference to fig4 through 7 it may be seen that the effective radius of the arc of the curved needle 44 is changed with each stroke of the needle through the fabric in particular the needle is caused to initially penetrate the fabric at a relatively shallow angle or small radius and as the needle penetrates the fabric the arc radius is increased in addition the axis of the arc may be moved away from the direction of needle penetration as the needle passes through the fabric referring to fig7 inspection of the relationship of rod positions 22 the needle shaft 40 supported by the needle base 42 and the needle 44 reveals that when the rod 22 is placed high.