Expanding mandrel

Claim 1

In a pipe belling mandrel, of the type comprising a cylindrical body adapted to receive thereon a circular gasket having an outer diameter, a shaped profile axially secured to the body to impress a bell-shaped configuration in a preheated end of a length of plastic pipe, a plurality of movable segments positioned intermediate the body and the profile, the segments being movable between a contracted position wherein the outer peripheries of the segments form a portion of the outer periphery of the body and an expanded position wherein the outer peripheries of the segments define an outer diameter that is greater than the outer diameter of the body, and forces other than atmospheric are applied to the mandrel to force the preheated pipe end against the profile and against the gasket, the improvement comprising a stop ring secured to the mandrel rearwardly of the segments, the stop ring having an outer diameter that is greater than said outer periphery defined by the segments when the segments are moved to their said expanded positions, the gasket being positioned on the body intermediate the stop ring and the said segments; a plurality of guide dowels secured within the mandrel interiorly of the shaped profile, the guide dowels being equally spaced about a central guide rod, the guide dowels each being radially outwardly and rearwardly inclined; each segment being simultaneously longitudinally and radially movable along a respective guide dowel between its said contracted position and its expanded position, each segment comprising an inclined forward surface and an arcuate outer surface, the outer surface of each segment extending rearwardly from the outer edge of the forward surface, the combined outer surfaces of the segments defining an outer periphery when the segments are moved to their said expanded positions of diameter greater than the outer periphery of the said gasket, the combined outer surfaces of the segments defining an outer periphery when the segments are moved to their said contracted positions of diameter equal to the outer diameter of the cylindrical body; the combined outer surfaces of the segments defining an outer periphery when the segments are moved to their said expanded positions of diameter greater than the outer diameter of the gasket; whereby the preheated end of the pipe will contact the inclined forward surfaces of the segments during belling and will be expanded to a diameter sufficient to allow the preheated pipe end to slide over the gasket when the pipe is applied to the mandrel and wherein the gasket will be removed from the mandrel and encapsulated in the belled pipe end upon completion of the pipe belling operation.