Method and apparatus for selectively heating discrete areas of surfaces with radiant energy

Abstract

Abstract A method and apparatus are disclosed for heating discrete areas of a surface bearing a thermoplastic or heat-activated adhesive or coating for the purpose of producing a thermal sealing of the surface with respect to another contacted surface as in the thermal sealing of flaps of paperboard containers. The method consists of the utilization of a radiant energy source focused onto the seal area to be activated. The radiant energy source is selected to have characteristics enhancing the focusability of its emissions, i.e., approximating a point source and having a relatively high proportion of visible and near visible range wavelength emissions. The method further includes treating of the discrete surface area with a marking absorbent of the focused radiant energy placed on the surface or by pigmenting the thermoplastic adhesive or coating itself, with the remainder of the surface being reflective to the focused radiant energy so as to control the absorption pattern of the focused radiant energy to thus cause it to be maximized in the confines of the discrete area. The focusing of the radiant energy pattern size is controlled in order to readily vary the size of the surface area upon which the radiant energy is focused so as to vary the area heated and/or to vary the intensity of heating of the area. The power output of the radiant energy source is also disclosed as being varied in accordance with the intensity of the heat energy required for the particular conditions under which the heating process is carried out, such as the speed with which the sheet material is moved past the radiant energy source, the absorbtivity or the pattern size required.

Inventors

• 👤 James J. Souder

Bibliographic Details