plate 10 and therefore the reference element for pivoting of the arbor 14 and the drum 20 has a relatively significant diameter in any case more significant than if these elements were pivoted directly at the level of their pivot axis grants the elements a better stability and greater precision in their movement this is beneficial not only for the pivoting of the drum 20 but also for that of the arbor 14 which undergoes stresses much better than the barrel arbors of the prior art also pivoted by a ball bearing but arranged directly at their center the efficiency obtained with a barrel as described above is substantially improved in relation to the barrels of the prior art in the illustrated embodiment the barrel arbor 14 is not mounted cantilevered in order to improve the precision of its positioning its end located at the side opposite the plate is pivoted by a third ball bearing 49 arranged using an arbor bridge 50 screwed on the plate traditionally this bearing 49 comprises a first outer ring 52 driven into the bridge 50 and a second inner ring 54 integral with the arbor 14 the ratchet wheel 30 tops the bearing 49 and the bridge 50 and is screwed.