is assembled in the lower surface 19 of the head 2 the pressure of the spring 51 and thus of the roller 28 can be regulated by selectively rotating the ring 53 the presser bar 14 is continually urged downwardly by a spring 56 disposed between the upper part of said presser bar and a regulating screw 57 assembled in an internally threaded sleeve 58 which is carried in the upper surface of the head 2 the pressure of the spring 56 and thus of the presser foot can be adjusted by selectively rotating the screw 57 when the shaft 47 is rotated the presser foot 36 and the roller 28 are simultaneously raised a lever 59 disposed adjacent the outer surface of the head 2 and attached to a relatively short shaft 60 by means of a screw 61 is provided for the purpose of raising the roller 28 independently of the presser foot the shaft 60 is provided with a plate 62 which carries a lug 63 that is disposed eccentrically of the axis of said shaft 60 the lug 63 is rotatable with the plate 62 by means of the lever 59 and is adapted to engage a projection 64 on the arm 39 so as to raise the rod 38 and the roller 28 operatively connected to the lower end thereof the roller 28 can be raised independently due to the fact that the slot 43 of the connecting rod 42 permits the arm 39 to be moved upwardly by the lever 59 without affecting the shaft 47 and the presser bar 14 the eccentric 7 is provided.