Casing construction

Claim 1

In combination with a vapor generator, structure defining a setting, a gas passageway situated within said setting, means for introducing combustion gases through said passageway, the setting having a roof formed of spaced first and second metal coverings, the first covering being disposed subjacent to the second covering and the space therebetween being at least partly filled with an insulating material, at least one upright member extending through said roof, the upright member being rigidly connected to said first covering, the improvement comprising means allowing thermal expansion and contraction of said first covering and upright member independent of the second covering, said last named means including having the second covering formed of a base portion having at least one elongated opening of generally rectangular configuration, the base portion including an upturned flange projecting from each of the sides defining said opening, at least two coplanar raised portions disposed above said flanges, said raised portions being spaced from one another, and said upright member extending between the flanges and raised portions in spaced relation thereto, plate means disposed above the raised portions and including an opening to accommodate passage therethrough of the upright member, said plate means being rigidly connected to the upright member and cooperating therewith and with the raised portions to cover said elongated opening.