Sealing device for packaging machine

A sealing device for a packaging machine wherein a strip film is delivered around articles being transferred to be packaged as they are horizontally arranged at equal intervals, said film being curled by tube making means to peripherally cover said articles while a frame supporting a pair of seal bars is reciprocated in the same direction as said articles to heat-seal said tube film, said sealing device comprising;

• means for transmitting the rotational movement of the main shaft of a servomotor mounted on said frame to said pair of seal bars, the forward and backward rotation of said main shaft being effective to open and close said pair of seal bars,
• cushion means for elastically pressing the seal bars against each other after said seal bars have closed with their opposed surfaces coming into contact,
• means for detecting by a current detector an impulse current to be applied to heat generating filaments stuck to the opposed surfaces of said seal bars, and transmitting the current value thereof to the controller,
• a rotational angle detector for feeding back the amount of rotational movement of the main shaft of the servomotor as a feedback pulse to said controller,
• arithmetic means for finding the gripping pressure exerted by the seal bars and corresponding to calorific power of said heat generating filaments from the collation between the feedback signal from said rotational angle detector and the transmitted signal from said current detector, and
• control means for transmitting an instruction signal to said servomotor on the basis of the result found by said arithmetic means in order to determine the amount of rotation of said servomotor main shaft.