276 are fixed with respect to the frame 34 the rollers 270 and 274 are adapted to permit translational in the x direction motion with respect to that frame 34 the rollers 270 and 274 are coupled by way of link 252 which is guided by pins 254 and 256 to permit the motion of the rollers 270 and 274 in the direction of the x axis a pneumatic actuator 280 and associated spring 282 is coupled between the frame 34 and the roller 274 and in its normally retracted position actuator 280 when energized is positioned as shown in fig4 together with rollers 270 and 274 as shown in that figure in its energized position when the solenoid 280 is de energized the rollers 274 and 270 are displaced so that the link 252 is positioned against pins 254 and 256 at its other extreme point with the result that the portion of belt 248 which was previously in the gap between the assemblies 46 and 48 is retracted therefrom permitting the needle 120 to pass between the respective belt assemblies at that point with this operation the coordinated switching of the belt 248 together with the other belts in the assembly as controlled by a spool value with a shuttle may be accomplished as the needle 120 is moved in the direction.