to control the temperature of the sealing jaw the thermocouple element 35 is connected to a temperature feedback signal analyzing circuit 49 and 49 u2032 which feeds the controller 47 the metal slitting wire 40 is fed a voltage signal by a voltage generator 50 which is also controlled by the controller 47 the controller 47 thus controls the magnitude of the voltage signal as well as the time duration thereof and this again is dependent on the type of materials being fused and slit accordingly it can be seen that with the present invention the temperature of each of the sealing ribbons as well as the slitting wire can be independently controlled and these are all adjusted whereby to achieve a seal having a desired quality as shown in fig6 a heat barrier strip 8 as shown in fig5 having holes 8 u2032 therein is secured to the flat rear face 21 of each of the sealing bars to insulate the hot sealing bars 19 and 19 u2032 from their support frame 23 as previously described the sealing jaw of the present invention seals the overlapped film sheets 9 and 9 u2032 from opposed sides thereof accordingly it is only necessary that the temperature of each of the ribbons be selected to melt the film sheet or sheets on its side if the other side has two film sheets or a different type of film sheet then the temperature of that ribbon will be different from the other as mentioned above 0037 fig7 a and 7b.