the apparatus 30 shown in fig1 for use in plastics sheet wrapping of rolled - up , web - shaped material 1 on a core tube 2 comprises a frame 3 on which a vertically slidable lifting table 4 containing two rollers 5 , 6 is mounted . the rollers 5 , 6 are rotatable by means of a motor ( not shown ). the rollers 5 , 6 moreover comprise holding arms 7 which are used for guiding the web - shaped material 1 into position and during tipping of the web - shaped material 1 . the holding arms are shown in different positions in fig2 . the frame 3 moreover mounts two horizontally slidable carriages 8 , 9 , on each of which two v - shaped closing yokes 10 , 11 , a welding head 12 and a cutting head 13 are mounted . the closing yokes 10 , 11 are movable vertically in slide guides 21 so that , seen from the end , they form an opening in the shape of a parallelogram 16 whose area may be made larger or smaller by moving the closing yokes 10 , 11 toward or away from each other . in fig2 the closing yokes 10 , 11 are shown in the open position in solid line and in the closed position in broken line . the ultrasonic welding head 12 , which is shown in fig3 is cylindrical with a circular cross - section and has an obliquely bevelled engagement face 14 , which is adapted to engage the plastics sheet material along the internal 17 or external 18 annular edge of the core tube at the end face 22 of the core tube during welding . the welding head is slidable vertically . in addition , it is movable horizontally so that it may be moved toward and away from the core tube . fig5 shows an embodiment in which a cone 40 is mounted in front of the ultrasonic welding head 39 , and this cone 40 positions the welding head with respect to the core tube 2 when the cone is driven into the core tube 2 . the cone 40 may be mounted such that it can slide with respect to the welding head 12 via guides 38 . hereby , after positioning , it is possible to advance the welding head 12 in a direction toward the core tube 2 , while the cone 40 is kept stationary within the core tube . like the welding heads 12 , the cutting means 13 may be moved vertically as well as horizontally . further , the cutting means may be moved around the end edge of the core tube . in a particularly expedient embodiment , as shown in fig4 the cutting means may be shaped as a turning saw 13 for cutting off excess , free plastics sheet material within the core tube after welding . the cutting means may also be provided as a cutting / milling head or knives which cut off the free plastics sheet material directly around the end face 22 of the core tube . it is shown in fig6 how two knives 41 are mounted behind a cone 42 which positions the knife device with respect to the core tube 2 . the knife device 43 is constructed such that the knives 41 are moved radially outwards when the shaft 45 of a motor ( not shown ) rotates in one direction of rotation , and radially inwards when the shaft 45 rotates in the other direction of rotation . for the shown closing of the end on the plastics sheet wrapped , rolled - up , web - shaped material , the roll 1 is placed on the rollers 5 , 6 and is guided into position via the holding arms 6 , 7 . then the lifting table 4 is raised / lowered to position the core tube 2 of the roll in alignment with the welding heads 12 via laser equipment ( not shown ). then the carriages 8 , 9 are run inwards toward their respective sides of the roll . the rollers 5 , 6 are subsequently caused to rotate , whereby also the roll 1 rotates . simultaneously , the closing yokes 10 , 11 are moved together around the excess plastics sheet parts at the ends , the closing yokes retaining the plastics sheet parts during continued rotation of the roll . in other embodiments ( not shown ), the closing yokes 10 , 11 and thereby the excess plastics sheet parts can be rotated so that the plastics sheet parts are kept together twisted in a desired manner after the closing yokes have moved away . then the twisted plastics sheet parts are welded together by means of welding equipment ( not shown ), and the excess plastics sheet parts are removed . then the welding heads 12 are advanced and urge the plastics sheet parts twisted and welded together into the ends of the core tube 2 , and the plastics sheet is is welded by means of ultrasound to the annular inwardly facing edge area 17 on the end face of the core tube 2 . welding takes place in that the welding head 12 , which is substantially in the shape of a truncated cone , is caused to oscillate with high - frequency oscillations , preferably 10 to 40 khz , whereby the plastics sheet is welded to the end face of the core tube , see fig3 and 4 . after welding , a complete plastics sheet weld will be provided on the end face . in connection with wrapping of carpet material the core tube normally has an outer diameter of 110 mm , and the dimensions of the mandrel 12 therefore correspond to this . then the welding heads 12 return , and the turning saw 13 is passed into the core tube 2 and cuts off the excess plastics sheet parts . when the knives 41 are to be used , the knife device 43 is inserted into the core tube 2 , while the knives 41 are displaced radially inwards . the motor is then caused to rotate in one direction of rotation , and the knives 41 will be displaced radially outwards and simultaneously cut off excess , free plastics sheet material within the core tube 2 . after cutting , the motor is caused to rotate the shaft 45 in the other direction of rotation , and the knives 41 will therefore be displaced radially inwards so that the knife device 43 can then be moved out of the core tube 2 . a hook device 43 may be placed in front of the knife device 43 , the hook device carrying along the excess plastics sheet material when the knife device 43 is moved out of the core tube . finally , the excess plastics material is sucked away via a central opening 23 in the turning saw 13 , which then returns . lastly , the carriages 8 , 9 return , and the lifting table 4 is run to the starting position , following which the roll 1 is tipped out of the apparatus during rotation of the holding arms 7 . fig4 shows another embodiment of the wrapping . in this case , the weld 18 is made on the outer edge 1b of the end face 22 of the core tube , and the cutting head 13 is being moved away from the core tube 2 . most frequently , the core tube 2 comprises a plastics tube , but in other embodiments it may be formed by , e . g ., a cardboard tube having an inner plastics coat or a cardboard tube having a plastics bushing at the end . many modifications are possible without departing from the actual idea of the invention . in the embodiment shown , the closing yokes are v - shaped . however , also more than two closing yokes shaped as , e . g ., straight lines or curves are conceivable .