45 and the guide lobe 16 39 of the previously mentioned cam 16 inserted in between these rollers slides relative to them so that each time the cam 16 completes one full rotation the shaft 45 and consequently also the movable knife 44 effect one vertical two way movement the top side of the plate that acts as the movable knife has drilled in it suitably positioned four holes 44 39 and these each time a cutting operation is performed are cyclically connected through a pipe 47 to a source of suction not shown in fig3 with each upward travel of the movable knife an understrip or shoulder piece is detached from the web n by a cut c as the web stands with the material stretching way past the cutting profile the severed understrip 4 attached by suction to the top side of the movable knife 44 via the holes 44 39 is thus lifted vertically from the cutting plane to an elevated position from there it can be transferred to devices outside the scope of the present invention such as for example those according to the aforementioned patent application in the name of the same applicant as herein briefly the transfer can be described as follows the transfer is carried out by an arm 48 pivoted to a vertical shaft 49 the arm 48 the extremity of which is also connected to a source of suction via a.