Abstract: The present invention comprises a machine having a fixed portion and fitted with a plurality of pneumatic cylinders and pistons, at least one of said cylinders and pistons is activated by a nominal-pressure supply, and which at least one cylinder and piston forms part of a subassembly which moves with respect to the fixed portion of the machine. There is a counter-pressure system for each working phase of the subassembly cylinder, including means for counteracting the nominal-pressure supply to reduce jerking movements of the subassembly during operation. Also a speed-control unit which has a variable throttling valve and an anti-return valve is affixed to the fixed portion of the machine separated from the movable subassembly. Flexible lines are connected between the subassembly cylinder and the speed-control unit so that the mass of the movable subassembly is reduced to further reduce the jerking motion of the subassembly.