which are both in the open position lateral wall 18 by tappet 22 contacting cam 24 fitted to rod 13 and lateral wall 19 by operation of shaft 27 subsequent movement of end wall 15 and external pusher 41 inwards of wrapping wheel 7 together with a simultaneous movement of lateral wall 18 and a subsequent movement of lateral wall 19 into their closed positions fig2 forms pocket 16 and causes insertion inside pocket 16 of group 5 and relative sheet of wrapping material 4 which as it is being inserted inside pocket 16 is folded about group 5 to define a narrow portion 42 contacting front surface 28 of lateral wall 19 and of a transverse dimension smaller than half the width of lateral wall 19 an inner portion 43 extending along end wall 15 and a lateral portion 44 extending along lateral wall 18 a portion integral with lateral portion 44 of the sheet of wrapping material 4 projects from pocket 16 and comprises an outer portion 45 which as pocket 16 travels along path p is folded fig2 in known manner e g by encountering an outer plate 46 onto group 5 into a position parallel to and facing inner portion 43 and a portion 47 projecting rearwards in the form of an extension of portion 45 outwards of and beyond pocket 16 in a direction crosswise to portion 42 portion 47 is of a transverse dimension greater than the transverse dimension of portion 42 and greater than the width of front surface 28 of lateral wall 19 minus the width of portion 42 pocket 16 together with relative group 5 and relative.