Method for welding plastic members

A method of butt welding aligned ends of a pair of plastic member with reduced waste material on the exterior surface of the joint formed between the plastic members, comprising the steps of:

• (a) placing a pair of plastic members in respective tools which each have opposing lower and upper dies that define opposing profile surfaces that conform to an exterior cross-sectional profile of the plastic member received and held therebetween, the tools further including opposing lower and upper plates disposed in spaced-apart relation to the lower die and the upper die, respectively, and movable mount means connecting the lower plate to the lower die and the upper plate to the upper die independently for lateral movement of the plates relative to the dies between a first distally spaced position to a second closely spaced position, the plates having opposing surfaces that conform to the exterior cross-sectional member of the plastic member for being received therebetween, the distal ends of the members being aligned with an exterior face of the respective plates;
• (b) moving a heat blade between the pair of tools;
• (c) moving the tools against the sides of the heat blade for melting the distal ends of the plastic members in contact therewith;
• (d) sealing the exterior of the plastic members from flow of molten plastic by moving the plates in contact with the heat blade laterally towards the dies from the first position to the second position as the distal ends of the aligned plastic members melt;
• (e) moving the tools away from the heat blade to take the plates out of contact therewith, with the plates moving from the second position to the first position relative to the respective dies to maintain the seal against flow of molten plastic to the exterior of the plastic members;
• (f) retracting the heat blade from between the pair of tools;
• (g) moving the tools together forcibly to move the plates laterally to the second position for compressingly fusing the melted distal ends of the plastic members together,
• whereby the plates move between the first and the second positions to seal between the heat plate and the profile from exterior flow of the melted plastic material which flows inwardly of the joint.