retracted and opens the chute 1 and the set of pressure rollers 15b pressing on the set of rollers 15a drives the letter along the letter path 10 in the embodiment shown the pair of arms 19 is articulated about the spindle 19a carried by the upper frame 5a substantially in the middle of its lower part this pair of arms extends towards the top of the upper frame on either side of the sharply bent chute 17 its upper end provides an abutment for the spindle of the set of rollers 15b the set of rollers 15b is held away from the set of rollers 15a or pressed resiliently against it below this upper end the pair of arms 19 carries the set of closure fingers which are inserted between the chute 17 and the entry chute from the interior side of the sharp bend in the chute 17 to isolate them or are retracted under the set or rollers 15a the pair of arms 19 extends beyond the pivot spindle into the lower frame from which it is operated each arm is substantially l shaped with the pivot spindle partway along the longer leg of the l the pair of arms 19 actuates the closure fingers 18 and the pressure rollers 15b the latter delayed relative to the former the folder module 11 the letter path 10 the empty envelope entry.