Abstract: A structural panel comprising one or a plurality of spaced sheet members has a frame around its edge. At least one body of material capable of screening the structural panel against fire is provided in the form of a chemically activated substance. The substance or substances are retained in an inoperative position in the vicinity of the structural panel and are released to an operative position in response to a predetermined rise of temperature wherein a body of material covers substantially one or more faces of the panel.

Abstract: In the severing of bodies of glass or vitrocrystalline materials by the application of a laser beam, the severing operation is improved by employing a beam of which at least the predominent wavelength is such that at least 10% of the beam energy penetrates the body to a depth of at least 0.2 mm.

Abstract: In the severing of glass by irradiating it with a laser beam along the line where it is to be severed, the quality and speed of the severing operation are improved by preliminarily scoring the glass along such line.

Abstract: An impact resistant panel composed of a group of at least three sheets of vitreous material bonded together via intervening layers of plastic material. According to one form of construction, the group includes a set of consecutive vitreous sheets of at least three different thicknesses which are arranged in order of thickness, and at least the first sheet, taken in the direction from the highest sheet thickness end of the set, is tempered. According to a second form of construction, the group includes a set of consecutive sheets of at least two different thicknesses arranged in order of thickness and at least two of the plastic layers are of different thicknesses and are arranged so that one of the layers having the smallest thickness is nearer the first sheet, taken in the direction from the thickest sheet, than is any other layer.