driven by roller 17 located on the storage car 8 by means of chain 24 which extends over a chainwheel on the axle of the roller 13 thus belt 11 is driven at the same speed as belt 14 the layer car 7 and the balance car 9 are connected together by a tension chain 25 the tension chain 25 is attached at 26 to the balance car 9 and at 27 to the layer car 7 and extends over a roller 28 mounted on the jib 10 of storage car 8 layer car 7 is driven by a car traction chain 29 which passes over fixed rollers 30 and 31 the upper bight of the car traction chain 29 is rigidly connected at 29a to the layer car 7 rotation of rollers 34 and 35 is effected by a measuring chain 36 stretched between two countersupports 37 the withdrawal rollers 34 35 or laying rollers are connected by transmission members 38 39 to chainwheels 40 41 via wheels 42 43 chainwheels 40 41 are provided with free wheel clutches respectively which operate in opposite rotary directions insuring that the rotary direction of the laying rollers 34 35 always remains the same when the layer car 7 changes direction the car traction chain 29 is driven by a reversible geared motor e g a dc motor a common drive unit is provided between the three cars.