US 4,362,688 A · Method for molding a plastic pipe

Abstract

A lower mold half is horizontally placed. The top surface of the lower mold half is provided with a first groove of any desired shape, one end of which is closed with the other end having a notch for allowing air to be blown in. An upper mold half has a bottom surface which matches the top surface of the lower mold half and which is provided with a second groove corresponding in shape to said first groove. Thus, when the upper and lower mold halves are brought into contact, there is formed a mold cavity defined by the first and second grooves. A discharging unit including a nozzle for discharging a parison is disposed above the lower mold half and the nozzle is so provided that it can rotate in either direction at a variable speed. At least one of the nozzle and the lower mold half is movably provided to lay a parison in the first groove.

Claims5

Dependent claims

A method for molding a plastic pipe comprising the steps of:

positioning a parison discharged out of a parison extruder having a nozzle into and along a first groove provided on a top surface of a bottom mold half and having at least one portion curved relative to a longitudinal axis of said first groove;
maintaining a predetermined distance between said extruder and said first groove during said positioning;
providing relative movement between said first groove and said nozzle along said longitudinal axis during said positioning;
rotating said nozzle over a predetermined angle about a nozzle center axis while positioning said parison along said curved portion such that said rotating is in a direction commensurate with a curvature direction of said curved portion;
placing a top mold half provided with a second groove on said bottom mold half, said first groove being in registry with said second groove to define a mold cavity;
and
injecting pressurized gas into the parison in the mold cavity for shaping as defined by the mold cavity.

4 more elements

Dependencies are inferred from the claim text.

Method for molding a plastic pipe

Life of this patent

Method for molding a plastic pipe

Life of this patent

Abstract

Claims5