a result the holder 34 is free to rotate as the turret 33 is indexed the motor 37 is now actuated to index the turret 33 by 60 u00b0 via the shaft 36 during the rotation of the turret 33 the sprocket 55 on each arm 47 extending between the positions a e rolls on the chain 56 such action effects over the speed reducer 53 and the shaft 48 a simultaneous rotation of the holder 34 through 90 u00b0 with respect to the arm 47 because of the absence of the chain 56 between positions e and a in the downstream direction the holders 34 on the arms which are then movable between these positions do not rotate during the indexing of the holder 34 the cylinder 63 fig5 at position e rotates the element 60 carrying the end of the chain 56 back into its original position within recess 59 so that the sprocket 55 on the arm 47 moving into position e is accurately stopped in this position at the same time the corresponding cylinder 63 located in position a oscillates its associated element 60 into the recess 59 so that the opposite end of the chain 56 is decoupled from the sprocket 55 that is connected with the arm moving from position f to position a in order to prevent any further rotational movement of the holders 34 as they enter the positions a e the spherical head 66 of the lever 65 disposed at.