Vacuum shaft furnace

The vacuum shaft furnace, used for the heat treatment of metal workpieces, contains a substantially cylindrical heating chamber (2) which is surrounded by a housing (1) and is closed at the top by a roof (12) and at the bottom by a floor (4), and the walls of which have closable openings for the passage of a cooling gas which can be circulated with the aid of a blower (31) via a heat exchanger (32, 33). To be able to generate, within the heating chamber (2), gas streams in a vertical direction and/or horizontal direction at various heights and at different points of the periphery, the roof (12) of the heating chamber (2) is joined on the outside to the suction side of the blower (31) by a hood (36) sealed off at the edge of said heating chamber, and the space between heating chamber (2) and furnace housing (1) is connected to the pressure side of the blower (31) laterally and below the heating chamber (2), closable outlet openings (25) being situated in the roof and closable inlet openings (16, 20) being situated in the side wall (13) and in the floor (4) of the heating chamber (2). The movable covers of the openings are actuated with the aid of lifting cylinders (24, 29 and 18, respectively). The inlet openings (16) in the side wall (13) are preferably equipped with single covers and lifting cylinders (18) to be actuated individually, so that individual cooling-gas streams can be introduced into the interior of the heating chamber (2) at different heights. Thanks to this design, selected regions of a batch can be exposed to streams of the cooling gas constantly or at specific times.