In an apparatus for successively making plastic bags, a laser beam irradiator irradiates laser beam onto webs of panel material and a body of zipper material to heat and melt the webs of panel material and the body of zipper material with the laser beam. The webs of panel material and the body of zipper material are fed intermittently at a speed predetermined to be changed by time. The irradiator is controlled on a feedforward control basis for the laser beam to be regulated in amount, the amount being calculated from the speed predetermined, to obtain a calculated value of amount. The laser beam is regulated in accordance with the calculated value to heat and melt the webs of panel material and the body of zipper material uniformly irrespective of the speed being changed.

Provided is an electric power control apparatus of an electrofusion coupling pipe using a conductive polymer composite as a heating element and a method of controlling electric power using the same. The electric power control apparatus supplies electric power to the electrofusion coupling pipe using a conductive polymer composite as a heating element to detect resistance variation of the conductive polymer composite and then controls electric power supplied to the synthetic resin pipe electrofusion coupling pipe on the basis of the detected resistance variation.

The present invention provides a thermal caulking device which cats quickly heat and cool an object to be caulked with low electrical power. Provided is a thermal caulking device which caulks a portion of a plastic part 7 as an object to be caulked, the thermal caulking device including: a metal tip 3 having a pressing part 3a which presses the object to be caulked and a heating rod 3c which is provided upright at a center part of the pressing part 3a; heating means 10c for heating the heating rod 3c; a cooling pipe 9 which cools the heating rod 3c; cooling fluid supply means 4 for supplying a cooling fluid to the cooling pipe 9; a holder 1 which holds the metal tip 3 and the cooling pipe 9 so that the cooling pipe 9 delivers the cooling fluid toward the heating rod 3c; and control means 6 for controlling the heating means 10c and the cooling fluid supply means 4, wherein the control means 6 heats the pressing part 3a from the heating rod 3c by the heating means 10c, and after the object to be caulked is thermally caulked by the pressing part 3a, supplies the cooling fluid from the cooling fluid supply means 4 to the cooling pipe 9 to cool the pressing part 3a from the heating rod 3c.