Patent ID: 7976766

Claim:
A mold for manufacturing, by blow molding or stretch-blow molding of a heated preform, a container made of thermoplastic material, in particular a polyolefin such as polypropylene, provided with an integral handle, said mold comprising at least two mold halves which are movable relative to one another, have respective mutual contact faces defining, in a closed position, a junction plane, have respectively two imprints which, joined together, define a molding cavity of the body and the shoulder of the final container, and comprise respectively two recesses which are substantially perpendicular to said respective contact faces and substantially mutually aligned in the closed position of the mold and which enclose two respective inserts forming pistons which can be moved pneumatically between a retracted position in which the two inserts are returned, at least for the most part, into their respective recesses and an extended position in which the two inserts are pushed together by pinching two given wall zones of the body of the container until said two wall zones of the body, which are then heat-welded together, are brought into mutual contact, wherein each insert comprises two pistons telescoped one within the other, namely a main piston or thrust piston having a centrally located front thrust face and, accommodated in said main piston, a coaxially arranged secondary piston or welding piston having a front face surrounding said front face of the main piston along a closed contour coinciding with the periphery of said wall zone of the body of the container, heating means being provided for keeping at least said front face of the secondary piston at the softening temperature of the thermoplastic material, the two pistons, the main piston and the secondary piston, being arranged in such a way that in a first operating phase, the main piston is moved from its retracted position to its protruding position, whereas the secondary piston remains retracted in said main piston, the front face of said main piston pushing said given zone of the wall of the body of the container, and in a second operating phase, the secondary piston is moved relative to the main piston from its retracted position to its protruding position in such a way that its hot front face rests against the periphery of said wall zone of the body of the container in order to soften the material thereof, to weld it peripherally with the wall portion pushed by the opposing piston, and at least to premark the perimeter of this wall zone.