Heating – Work chamber having heating means – Having means by which work is progressed or moved mechanically
Reexamination Certificate
2002-01-29
2003-09-23
Wilson, Gregory (Department: 3749)
Heating
Work chamber having heating means
Having means by which work is progressed or moved mechanically
C432S143000, C432S163000, C266S176000
Reexamination Certificate
active
06623269
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a thermal treatment apparatus used for a thermal treatment of a starting material, an intermediate product or a final product.
BACKGROUND ART
Various thermal treatment processes such as a heating process and a cooling process are employed in the processes of manufacturing various products such as a plasma display panel, a solar battery panel, a resistor chip and other devices and electronic parts. Numerous effects achieved by a thermal treatment are known. Specifically, drying, dehydration, calcination, reaction acceleration, surface modification, sealing, degassing, annealing and so on are known.
In a case where a heating furnace is used as a thermal treatment apparatus, the thermal treatment apparatus generally has a plurality of thermal treatment chambers arranged in the direction of transporting an object to be treated. Each thermal treatment chamber has a space provided therein in which the object is subjected to a thermal treatment, namely a thermal treatment zone. A heating furnace generally has a temperature raising zone (temperature raising chamber) in which the object is heated to rise in temperature, a thermostatic zone (thermostatic chamber) in which the object is maintained at the raised temperature, and a temperature lowering zone (temperature lowering chamber) in which the object is cooled down to decrease in temperature, as the thermal treatment zones. The object to be treated is subjected to predetermined thermal treatment processes while passing through each zone in the order described above. Typically, heat is applied in the temperature raising zone, while such an amount of heat is supplied which compensates for heat dissipation in the thermostatic zone, and heat is removed in the temperature lowering zone.
Therefore, the temperature raising zone and the thermostatic zone in which heat is applied to the object to be treated may also be called a heating zone. And the temperature lowering zone in which heat is removed from the object may also be called a cooling zone. The temperature lowering zone may also be called a slow cooling zone or a quenching zone depending on the decrease in temperature of the object which decrease is effected during the period from the entry of the object into the zone to the exit of the object from the zone (temperature decreasing rate). The slow cooling zone is generally a zone in which the temperature of the object entering the zone is lowered at a rate, for example, from several degrees to several tens of degrees Celsius per minute. The quenching zone is generally a zone in which the temperature of the object entering the zone is lowered at a rate of several hundreds of degrees Celsius per minute or higher.
Dimensions of the heating zone and the cooling zone are determined according to thermal treatment conditions on the basis of a throughput of the object to be treated, such as the time required for heating, cooling rate and a temperature of the object at the exit and the floor space required to install the thermal treatment apparatus.
In the case of a thermal treatment apparatus having a plurality of thermal treatment chambers, it is necessary to maintain the temperature in the thermal treatment chamber (namely the temperature in the thermal treatment zone) at a predetermined level so as to ensure that the predetermined thermal treatment effect is achieved in each of the thermal treatment chambers. For this purpose, temperature in the thermal treatment chamber is controlled by means of proper heating or cooling means and a temperature monitor.
The thermal treatment apparatus having a plurality of thermal treatment chambers may be a thermal treatment apparatus wherein an object to be treated is transported intermittently through the thermal treatment zones of the thermal treatment chambers, or a thermal treatment apparatus wherein an object to be treated is transported continuously through the thermal treatment zones of the thermal treatment chambers. An example of the thermal treatment apparatus wherein the object is transported intermittently is disclosed, for example, in Japanese Kokai Patent Publication No. 11-142061.
In the thermal treatment apparatus described in this publication, thermal separation between the thermal treatment zones is ensured by shielding each thermal treatment zone from other thermal treatment zones so that the thermal treatment zone will not be thermally influenced by the adjacent thermal treatment zones. Specifically, this thermal treatment apparatus has a shutter apparatus comprising a plate-like shutter disposed between heating zones and a pair of thermal insulating walls disposed to sandwich the shutter. The shutter is positioned at a shielding position where the heating zones are shielded from each other or at a retracted position where interference with the object being transported is prevented. That is, the shutter is placed at the retracted position when the object is moved between heating zones, and is placed at the shielding position when the object is moved into the heating zone. The object introduced into the heating zone is caused to stand still in the heating zone or to move back and forth therein so as to be subjected to a thermal treatment into a predetermined temperature.
In this thermal treatment apparatus, the shutter shields the heating zones from each other, while a thermal insulation effect is provided by the thermal insulating walls disposed at the border between the heating zones and an air layer formed between the thermal insulating walls. Thereby, each heating zone is thermally influenced as little as possible by the other adjacent heating zones. The air layer formed between the thermal insulating walls also prevents heat from being directly transmitted from the high temperature heating zone to the low temperature heating zone. Accordingly, in accordance with this thermal treatment apparatus, a temperature in each heating zone can be quickly controlled to the predetermined level after transporting the object intermittently and closing the shutter. In other words, this thermal treatment apparatus ensures independence of each thermal treatment zone by means of the movable shutter and the thermal insulating walls. This provides such advantages as the quality of the object can be assured and the total length of the thermal treatment apparatus can be made smaller.
Now the thermal treatment apparatus wherein the object to be treated is transported continuously is described below.
As an example of thermal treatment apparatus having a plurality of thermal treatment chambers wherein the object is transported continuously, there is one that applies a thermal treatment indirectly to the object while transporting the object in the thermal treatment chamber, called a muffle, which has a tunnel structure and is heated or cooled by proper heating or cooling means. The object is transported by conveyance means such as a mesh belt conveyor or a roller hearth. This type of thermal treatment apparatus is often called a muffle furnace or a muffle structure heating furnace. In the muffle furnace, the thermal treatment zone is defined by the muffle wall, and the thermal treatment zone is a thermal treatment atmosphere that is maintained at a predetermined temperature by heating means or the like installed outside the muffle.
The “thermal treatment atmosphere” refers to a space in which an object to be treated is placed. Heat is applied to or removed from the object placed in this space by means of a gas contained in the space, a heating device, cooling device and/or the wall that defines the space. The “thermal treatment atmosphere” is also referred to merely as an “atmosphere”. The gas included in the thermal treatment atmosphere is called an “atmosphere gas”.
In the muffle furnace, the object is carried into the thermal treatment atmosphere and is desirably heat-treated by being heated or cooled indirectly via the inside surface of the muffle wall. Since the muffle furnace does not have heating means or the like in the thermal treatment zone, une
Naka Hiroyuki
Tsutsui Yuji
Wenderoth , Lind & Ponack, L.L.P.
Wilson Gregory
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