Heated tool for plastic forming or welding, includes heating element running through series of U-shaped ceramic insulators held in dovetailed slot in tool surface

摘要

The tool includes ceramic insulators (7) arranged in series, in a groove (8). The dovetailed groove cross section, tapers down towards the upper surface (16) of the tool, and is matched by the shape of the insulators. They part-surround the heating element (10). Insulator thickness decreases towards its ends; seen from above, the insulators appear rounded. Sidewall inclination is preferably about 10[deg] . The insulators have two limbs (14, 15) enclosing the sides of the heating element (10). The limbs form a groove. The base of the groove and the side limbs, define a free space (18) for a heating element which deforms under pressure. The maximum side extent of the element exceeds the smallest spacing (A) between the limbs, at the opening between them. The element is pressed into its seating in the insulators. It is clipped into them. When inserted, the top of the element projects from the tool. The insulators extend up to a position below the top surface (16) of the tool. The spacing between the insulators and the top of the tool is preferably 0.1-0.4 mm. The insulators are separated and when installed, the gap between them is preferably about 0.5 mm. The gap is positioned centrally below the element.