Watermark mold, for fitting at the fourdrinier of a papermaking machine, is of a shape memory metal alloy at least at the holding tabs, to be inserted at one temperature and anchored by shape distortion at a second temperature

摘要

The mold (10), to form a watermark in paper, is secured to the fourdrinier by holding tabs (11) of a shape memory metal alloy. The watermark mold is fitted to the fourdrinier at a temperature where the holding tabs pass through the fourdrinier. The mold temperature is raised to a level where the holding tabs distort spontaneously to anchor the mold at the fourdrinier. The mold to form a watermark in paper, at the fourdrinier, uses the one-way effect of the shape memory metal alloy by a mechanical distortion before fitting to the fourdrinier, or the two-way effect of the metal by training the holding tabs in advance to give the required distortion effect to anchor the holding tabs in place by heat. An Independent claim is included for a watermark mold, with holding tabs, to be anchored at the fourdrinier. Preferred Features: The shape memory metal alloy, at least for the holding tabs, has a durable and malleable martensitic composition at room temperatures and at lower temperatures of 0 deg C or less. At higher temperatures, the composition of the metal alloy changes into an austenitic composition, and takes up its original shape imposed on it before shaping in the martensitic condition. By changing the temperatures, the metal alloy can be made to adopt two different shapes where the first condition is generally in a martensitic composition and the second is austenitic and partially martensitic.