Abstract: A system is provided for heating and thermally conditioning glass sheets, wherein sheets are conveyed individually or in groups or loads through a tunnel-type heating furnace and thermal conditioning area upon a series of aligned rollers. The rollers are driven in groups, with each group having an independent drive mechanism. The independent drive mechanisms are provided with interrelated controls whereby the system is controlled in zones of one or more groups of rolls. A sheet or load of sheets is advanced into a zone, and the rolls within that zone are then driven to convey the sheet or load in an oscillating forward and reverse manner to oscillate the glass within the zone. The oscillation proceeds according to a predetermined schedule whereby the distances travelled by the sheet or load on each forward and reverse stroke varies according to a predetermined pattern so that the contact points between the glass and rolls is different upon each reversal in direction.

Abstract: An elongated, horizontal tunnel-type furnace for heat treating workpieces carried in succession therethrough. The furnace is of modular construction and comprises a series of contiguous individual modular sections that define a tunnel-type enclosure. Each modular section comprises a stationary lower enclosure section and an assembled vertically retractable upper enclosure section. The upper enclosure sections are supported along opposite sides by a plurality of spaced, free-standing lifting devices. A screw-jack is associated with each lifting device for raising and lowering the upper enclosure sections relative to the lower enclosure sections. The upper enclosure sections may be raised and lowered individually or joined together and moved as a unit.