Method and apparatus for heat sealing plastic members

A heat sealing apparatus for providing a smooth and wrinkle-free bond between the adjoining surfaces of two plastic members to form a self-supporting assembly, the combination comprising:

• a seamless, tubular elastic heating element encircling the plastic members and positioned about the surfaces to be bonded, said heating element having a bonding position in which said elastic heating element is under tension and having an elastic flexible inner surface engaging and conforming to the external configuration of the plastic members, and a non-bonding position wherein its elastic flexible inner surface is spaced from the plastic members;
• said heating element includes a uniform dispersion of particulate material integrally disposed therein capable of generating heat in response to a source of energy and operable with the expansion and contraction of the element;
• an induction heating means for raising the temperature of the particulate material to heat said adjoining surfaces to a bonding temperature;
• and
• hydraulic positioning means coupled to the heating element and disposed circumferentially thereabout for moving the heating element between its respective bonding and non-bonding positions whereby in said bonding position the heating element is contracted about said plastic members to establish a bonding pressure thereon and said elastic flexible inner surface totally conforms to the configuration of the plastic members, and in said non-bonding position the heating element is elastically expanded outwardly of said bonding position to permit relative movement of said plastic members with respect to the heating element.