Metallurgical apparatus – Means treating solid metal – Having evacuated chamber
Reexamination Certificate
2002-01-25
2004-06-15
Kastler, Scott (Department: 1742)
Metallurgical apparatus
Means treating solid metal
Having evacuated chamber
C432S138000
Reexamination Certificate
active
06749800
ABSTRACT:
FIELD OF THE NVENTION
The invention relates to an arrangement for transporting metallic work pieces, especially during a heat treatment process, which is equipped with a heat-insulated transport chamber designed to hold the work pieces, means for loading and unloading the work pieces, and transporting gear for moving the transport chamber. The invention further relates to a system for heat treating metallic work pieces, which is equipped with at least two treatment chambers in which the work pieces may be heat treated. Furthermore, the invention involves a method for transporting metallic work pieces during a heat treatment process, in which the work pieces are transported within a heat-insulated transport chamber between at least two treatment chambers in which the work pieces may be heat-treated.
DESCRIPTION OF THE RELATED ART
In order to generate specific properties for work pieces, such as a high degree of hardness or a high capacity of resistance to wear, metallic work pieces are usually subjected to a thermal or thermochemical heat treatment process. The heat treatment alters the microstructure of the work pieces, lending them the desired properties. In addition to the general processing parameters of pressure, temperature, and duration of treatment, the atmosphere in which the heat treatment is conducted is of particular importance to the outcome of the treatment. A number of processes are known in the art by which work pieces can be exposed to various atmospheres in order to obtain the desired treatment results. In such processes the work pieces are carried, one after another, to a plurality of treatment chambers in a heat treatment system. The individual treatment chambers are ordinarily connected to one another via a transfer canal, which serves to protect the work pieces during transport from environmental influences that could produce undesirable effects on the treatment results achieved up to that point. To this end, the transfer canal can be either filled with a protective atmosphere, such as is known, for example, from DE-A-43 16 841, or evacuated of air, such as is proposed in FR-A-2 771 754.
The disadvantage of transfer canals of this type is that the configuration of the course of the heat treatment system can be varied to only a limited extent. Further, dismantling such heat treatment systems is relatively costly, even in cases involving modular construction such as is known from FR-A-2 771 754. In terms of economy, it is also most unsatisfactory that maintenance work on individual treatment chambers, and especially on the conveyor car in the transport canal, necessarily requires the temporary shutdown of the entire heat treatment system.
Further, from U.S. Pat. No. 5,567,381 a heat-treatment system is known which is equipped with a vacuum furnace, a transfer canal, and a movable transport chamber. The transport chamber can be coupled to the vacuum furnace via the transfer canal. The transport chamber, which is heat-insulated from the outside and is equipped with a hermetically sealed door, is further equipped with a heating unit for heating the work pieces, and a lifting device for loading and unloading the work pieces. To transfer the work pieces, which have been heated to a certain temperature in the vacuum furnace, to a further treatment chamber, such as a quenching chamber, the transport chamber is coupled to the transfer canal and preheated. Both the transfer canal and the transport chamber are then flooded with an inert gas, until they reach a pressure that is greater than the ambient pressure, in order to prevent air from entering the transfer canal or the transport chamber from the outside. The work pieces in the vacuum furnace are then cooled to the temperature prevailing in the transport chamber, and the vacuum furnace is flooded with an inert gas. When the same pressure level has been reached in the vacuum furnace and in the transfer canal or transport chamber, the door of the vacuum furnace is opened, and the work pieces are loaded inside via the lifting device that is part of the transport chamber.
With the transport chamber described above, it is possible to transport heated work pieces from one treatment chamber to the next while exposing them to an atmosphere of inert gas, thus preventing an undesirable oxidation of the work pieces. Although the heat treatment system described in U.S. Pat. No. 5,567,381 offers a greater degree of flexibility than the heat treatment systems discussed above involving a stationary transfer canal, it carries with it the disadvantage that in coupling the transport chamber to the vacuum furnace, the transport chamber, the transfer canal, and the vacuum furnace are all flooded with the inert gas. Apart from the fact that providing the inert gas for such a system is highly costly, the inert gas also presents an obstacle to a continuous heat treatment process during transport of the work pieces from treatment chamber to treatment chamber. This is because the change in the atmosphere in the vacuum furnace triggered by the unavoidable flooding of the furnace with inert gas not only presupposes the conclusion of the heat treatment process in the vacuum furnace, but also is unavoidably connected with a cooling of the work pieces, due to the fact that the protective gas is not preheated. The latter is most disadvantageous for high-temperature heat treatment processes, in which, as a rule, no notable temperature fluctuations can be permitted.
SUMMARY OF THE INVENTION
The object of the invention is to provide an arrangement and a method for transporting metallic work pieces, and a system for heat treating these work pieces, which will enable a comparatively flexible and efficient transport of the work pieces among a plurality of treatment chambers during a heat treatment process.
This object is attained in accordance with the invention in an arrangement having the characteristic features described above, in that the transport chamber is designed to be vacuum-tight and can be evacuated of air to create a vacuum that will protect the work pieces from environmental influences.
An arrangement of this design, in comparison to the prior art stationary transfer canals, enables the flexible transport of the work pieces during a heat treatment process. For example, individual treatment chambers in a heat treatment system can be excluded from the process cycle to allow maintenance or repair work, without the other treatment chambers being involved. Further, with the arrangement specified in the invention, existing heat treatment systems can be expanded to include additional treatment chambers, without great expense.
Furthermore, this type of arrangement enables a considerably more efficient process due to the fact that, rather than flooding with inert gas, a vacuum is created in the transport chamber in order to protect the work pieces from undesirable environmental influences, such as oxidation caused by the introduction of oxygen. In contrast to the movable transport chamber specified in U.S. Pat. No. 5,567,381, with the arrangement specified in the invention it is possible to continue the heat treatment process inside the transport chamber during the transport of the work pieces from one treatment chamber to the next, without any noticeable change in temperature. In addition to the time that is saved with such an arrangement, providing an economic advantage, the arrangement is further characterized by its particular suitability for use with high-temperature heat treatment processes.
It is especially advantageous for the arrangement to be equipped with a vacuum pump for evacuating the air from the transport chamber. This offers the advantage that the arrangement is self-sufficient in terms of the evacuation of the transport chamber, and is thus not dependent upon the specific design of the treatment chambers. The transport chamber can thus dock, for example, with both vacuum furnaces and atmospheric furnaces, or with cooling chambers. Furthermore, providing the arrangement with a vacuum pump makes it possible for the transport cha
Bless Franz
Müller-Ziller Jörg
Cantor & Colburn LLP
Ipsen International GmbH
Kastler Scott
LandOfFree
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