previously described with reference to fig1 and 2 can now be momentarily applied against the top part on the upstream side of the gluing cylinder 5 as can be seen in fig3 and 4 the roller 1 carrying its two previously described sleeves 2 is supported by two levers 22 each lever being articulated on a pivot 23 fixed in each frame 24 and controlled by a jack 25 which is also articulated on the corresponding frame 24 the jacks 25 make it possible to obtain an upper position in which the roller 1 is not applied against the gluing cylinder 5 thus permitting the free passage of the glue deposited on the cylinder after dipping into the tank 15 in the lower position the roller 1 comes to bear against the cylinder 5 by means of its sleeves 2 thus limiting the gluing zone to the distance l which separates the two doctor sleeves 2 on the generatrix of contact of the roller 1 and the gluing cylinder 5 the roller 1 can be driven rotationally by means of the irreversible motor 7 and the pinion and chain transmission 26 it is thus possible to adjust the distance l desired between the two sleeves 2 before.