Abstract: A method for repairing a hot-blast, long-time cupola furnace by removing residual slag and relining the cupola furnace including feeding liquid nitrogen to the cupola furnace immediately at the end of a smelting operation and simultaneously with the feeding of the liquid nitrogen, removing residual slag from the furnace. The furnace is cooled with liquid nitrogen until the furnace reaches a temperature of less than or equal to 40.degree. C. after which the furnace is relined with fresh refractory tamping compound.

Abstract: A crawler unit for coupling to a wheelchair, especially for climbing stairs, comprises an undercarriage having power-driven tracks and an adapter for securing the wheelchair in a rearwardly tilted travelling position. In order to enable the wheelchair user to couple and decouple and maneuver the wheelchair by himself, the adapter which includes a male coupling member for mating engagement with a complementary female coupling member mounted on the wheelchair is connected to the crawler unit through lifting means adapted to be operated by the wheelchair user via actuating or control elements for selectively lifting the wheelchair relative to the crawler unit and lifting the crawler unit while the wheels of the wheelchair remain on the ground, such operation being possible both in position of the wheelchair.