tractor drive system 58 for instance with the stepper motor 39 s controller discussed above in fig3 b so that the nozzle 20 is lowered after the web 12 is advanced this arrangement is not the only manner in which the nozzle 20 may be inserted and retracted from the balloon neck 56 this arrangement is for explanatory purposes only and is not intended to limit other possibilities the portion of the web 12 containing the balloon 18 to be filled rests on a support plate 24 this plate 24 supports that section of the web 12 when the nozzle 20 is inserted into the balloon neck 56 the plate 24 is grooved to allow passage of the balloon 18 to the nozzle 20 a tension box 22 is mounted on the support plate 24 this box 22 creates tension in the web 12 so the pins 28 on the tractor drive 58 can grab the advancing web 12 as noted above the wheels 44 of the tractor drive 58 move a precise distance at each step which ensures that uninflated balloons 18 are in registration with the nozzle 20 if there was too much play in the web 12 and the pins 28 could not grab the perforations 14.