45 a shaft 67 extends up the main frame 52 and movably on it but engaged for rotation with it is a gear 68 which meshes with a corresponding gear 69 connected to a shaft 70 which extends to a worm 71 which mates to a worm wheel 72 a shaft 73 is secured to the worm wheel 72 and is supported on the support frame 51 by a support 74 at the end of shaft 73 remote from the cylinders 43 45 is an air cylinder 75 which is capable of moving the shaft 73 axially at the other end of the shaft 73 is a clutch plate 76 which engages a corresponding clutch plate 77 on a stub shaft 78 extending from the plate cylinder 45 the clutch plates 76 77 and their attached shafts 73 78 pass through an aperture 79 in the main frame 52 at the end of the plate cylinder 45 are gears 80 which mesh with corresponding gears 81 on the blanket cylinder 43 thus when the air cylinder 75 moves the shaft 73 so that the clutch plates 76 77 are in engagement drive from the shaft 67 is transmitted via gears 68 69 shaft 70 worm 71 worm gear 72 shaft 73 clutch plates 76 77 and the stub shaft 78 to the plate cylinder and hence via gears 80 81 to the blanket cylinder when the air cylinder 75 moves the shaft 73 to disengage the clutch plates 76 77 no drive is transmitted furthermore this movement of the shaft 73.