Method and device for welding two hollow profiled rods made of plastic

A method for welding two hollow profiled rods of plastic to form a window frame, the method comprising the steps of:

• providing a first hollow profiled rod having a connecting surface and a second hollow profiled rod having a connecting surface, the first and second hollow profiled rods being made of plastic;
• performing a first heating step of heating the connecting surface of the first hollow profiled rod and the connecting surface of the second hollow profiled rod to a predetermined temperature by:
• inserting a welding plate having first and second opposite sides between the connecting surfaces of the first and second hollow profiled rods;
• and performing a first pressing step of pressing the connecting surface of the first hollow profiled rod against the first side of the welding plate and pressing the connecting surface of the second hollow profiled rod against the second side of the welding plate;
• wherein the first pressing step causes the formation of an outer bead of plastic material and an inner bead of plastic material adjacent the respective connecting surface on both of the first and second hollow profiled rods;
• and wherein each outer bead is formed on a respective side of the first and second hollow profiled rods which corresponds to a visible surface of the window frame;
• removing the welding plate from between the connecting surfaces of the first and second hollow profiled rods;
• after removing the welding plate, performing a second pressing step of pressing only the outer bead on each of the first and second hollow profiled rods slightly inward, wherein the second pressing step also forms an oblique edge adjacent the respective connecting surface of both of the first and second hollow profiled rods;
• after the second pressing step, removing each respective outer bead together with each respective inner bead from both of the first and second hollow profiled rods, and then joining the connecting surfaces of the first and second hollow profiled rods together.