thereon a torsion gear 28 is secured to and rotates with main shaft 27 and engages with a gear 29 for controlling lock mechanisms 13 and 15 the torsion gear 28 transmits rotation of main shaft 26 to gear 29 in a normal 1 1 ratio locking cams 30 31 are formed on torsion gear 29 with different angular positions for controlling lock mechanisms 13 15 respectively a needle lock control follower 33 with a pawl 34 and a similar feed lock control follower 35 are pivotally mounted on bracket 2 by means of a pin 32 and are each brought into engagement with the needle lock control cam 30 and the feed lock control cam 31 by tension springs 36 37 respectively needle lock control follower 33 has a collar 38 at its center of rotation an adjusting plate 39 is mounted on collar 38 and is secured to the follower 33 at a hole 40 on plate 39 one end of a needle lock element 41 is rotatably mounted on collar 38 of needle lock control follower 33 the needle lock element 41 is provided at its other end with chamber 42 to receive a compression spring 43 which protrudes in part out of chamber 42 the protruding end of spring 43 is held by an upper projection 44 of needle lock control follower 33 when pawl 34 of needle lock control follower 33 engages the lower lobe of needle lock control cam 30 the intermediate projection 45.