| 摘要 |
A counter-top or free-standing cooking unit with a top surface of natural stone, such as granite, is made especially resistant to cracking and fracture caused by mechanical or thermal stress. The natural stone's perimeter is cut and holes cut to match the diameters of the heating elements to be installed. The stone is preferably annealed for a suitable time at a suitable temperature to relieve stresses introduced by cutting. A reinforcing plate material is selected to have sufficient tensile strength, good thermal conductivity, and a thermal expansion coefficient that matches to some extent the stone's lateral thermal expansion. The plate may be a laminated composite of several metals, chosen such that the thermal expansion of the laminate matches that of the stone as closely as possible. The plate is cut smaller than the stone slab's outer dimensions. Holes are cut in the metal plate, preferably smaller by a predetermined amount than the holes cut in the stone, and large enough to accommodate the gas or electrical feeds to the heating elements. The metal plate is aligned and cemented to the rear surface of the stone, with a thin layer of suitable thermally stable adhesive such as epoxy adhesive. Thin slots for preventing fracture may be cut between the holes and the edge of the stone. The stone is preferably incorporated into a laminate comprising a thin top layer of stone previously prepared with a thin backing layer of perforated-metal, expanded metal, metal mesh, or Fiberglas bonded to it. Also, the stone preferably extends a desired amount laterally along an existing counter, to provide a stone-surface preparation area not occupied by heating elements. The plate may extend under the laterally-extending part of the stone, to a distance from the nearest heating element. In such embodiments there may be a gap, slot, or series of slots in the metal plate, providing thermal resistance to keep the stone preparation surface area relatively cool.
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