the inner periphery 13a of the wheel 13 thereby to transmit the rotation of the pulley 13 to the upper shaft 1 therefore if the clutch lever 18 is turned in the clockwise direction against the action of the torsion spring 23 the roller is displaced from the higher part of the slope 24 to a lower part of the groove 19 in which the roller 22 is spaced from the inner periphery 13a of the pulley in this case the rotation of the pulley 13 is not transmitted to the upper shaft 1 as shown in fig1 an intermediate pulley 25 is provided the pulley 25 is connected to a machine drive motor not shown by means of a belt 26 the pulley 25 is formed with a coaxial small pulley 25a which is connected to the pulley 13 by means of another belt 27 so that the driving power of the machine drive motor may be transmitted to the pulley 13 thus the pulley 13 is rotated in the direction as indicated by an arrow a as shown in fig1 and 7 a bracket 28 for a machine stopping mechanism is secured to the machine housing 2 by means of upper and lower screws 29 30 the screw 29 has a nut 29a mounted at the intermediate part thereof a stop lever 31 is turnably mounted on the screw 29 on one side.