Pusher type furnace for heat-treating charges

In a pusher type furnace comprising a heat treatment chamber through which a row of charge holding devices may be pushed from an inlet to an outlet along a rectilinear direction of charge travel, a method for heat treating charges carried by said charge holding devices, said method comprising the steps of

• a) entering said charge holding devices into said heat treatment chamber at a first end thereof and pushing said charge holding devices together for said devices to form at least one row and to be in contact with each other in the direction of charge transfer;
• b) moving said row of charge holding devices in said direction of charge transfer in tune with an overall furnace cycle each such forward movement continuing until the end of the pusher part of each such cycle;
• c) thereafter moving a charge holding carrier means with an actuator coupled to the charge holding carrier means to separate each such row of charge holding devices into at least two sets creating a gap in the direction of charge transfer between each two such sets, whereby at least one of each two adjacent sets is moved relative to the other set by a predetermined distance;
• d) separating said heat treatment chamber into compartments by closing a door across each gap between two such adjacent sets;
• e) selectively heat-treating the charges held by at least one of said isolated sets of charge holding devices;
• f) opening the door across each gap between each two adjacent sets;
• g) joining the separated sets of charge holding devices by moving at least one charge holding device carrier means relative to another charge holding device carrier means wherein said one charge holding device carrier means is moved by an actuator coupled to said one charge holding device carrier means and
• h) carrying out the next following pusher part of the overall furnace cycle to move each row of charge holding devices in said direction of charge travel.

A pusher type furnace for heat-treating charges carried by charge holding devices and moved through said furnace in a cyclic mode in a direction of charge travel, said pusher type furnace having

• a heat treatment chamber to hold at least one row of adjoining charge holding devices;
• first door means to close and to open an inlet of said heat treatment chamber;
• second door means to open and to close an outlet of said heat treatment chamber;
• pusher means for the cyclic transfer of said charge holding devices through said heat treatment chamber;
• charge holding device carrier means to support said charge holding devices in said heat treatment chamber, said carrier means having at least three sections arranged substantially one behind the other in said direction of charge travel, the upstream and the downstream sections being adapted to be moved in said direction of charge travel to create a gap in the row of charge holding devices between each two adjacent sections, wherein the upstream section is moved by an actuator coupled to the upstream section and the downstream section is moved by an actuator coupled to the downstream section;
• and
• third door means to separate said heat treatment chamber into at least three compartments, said third door means being associated with each such gap and adapted to close across each such gap between each two successive pushing parts of the overall furnace cycle,
• the heat treatment chamber thereby being selectively dividable into at least three heat treatment zones.