Patent Application
20130313763
This application claims the priority of German Patent Application, Serial No. 10 2012 104 537.2, filed May 25, 2012, pursuant to 35 U.S.C. 119(a)-(d), the content of which is incorporated herein by reference in its entirety as if fully set forth herein.
The present invention relates to a furnace for the thermal treatment of light metal component, and to a method for the thermal treatment of light metal components.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
The use of sheet metal components for the production of automotive components has been known for many decades. The sheet metal components are first formed and then combined to single modules or to an entire body. Motor vehicle bodies are nowadays mostly formed as self-supporting bodies, so that the sheet metal components not only perform aesthetic or shaping tasks, but must also have stiffness properties to impart to the vehicle body sufficient rigidity during use.
Demands on the crash behavior are also placed on the structural vehicle components, which must dissipate impact energy into deformation energy through targeted deformation in the event of a collision.
Steel represents a preferred material due to its advantageous manufacturability accompanied by high rigidity. In particular, the hot-forming and press hardening technology gives the steel high-strength or even ultra-high-strength properties, so that the specific weight of the components could be further reduced, while simultaneously increasing the strength values.
Today, however, not only aesthetic and safety expectations are imposed on motor vehicles, but also ecological and economic aspects for operating the motor vehicle have become rather important. So it is especially important that the vehicle has low fuel consumption with simultaneously low CO2 emissions. For this purpose, there are various approaches, for example the use of new drive techniques such as the hybrid drive, or a particular shape giving the motor vehicle a low air resistance.
Another approach is the use of light metal components to reduce the specific weight of the vehicle body and thus of the entire vehicle. In particular, light metal components made from aluminum alloys are used.
For certain applications, for example with high degrees of deformation or when setting specific strength values in aluminum components, the plates must be thermally treated prior to forming and/or at intermediate steps during forming and/or after forming.
Continuous furnaces known in the art include a transport system on which sheet metal components or sheet metal plates are continuously transported through a furnace and heated inside the furnace. Several approaches exist, for example infrared heating or induction heating of the component or the plate inside the furnace.
However, when such furnaces are used for light metal alloys, some methods are inefficient because the aluminum reflects, for example, the heat radiation or the methods are technically impractical, since e.g. the shaped plates or components can only be heated unevenly and thus severely distort; more often, however, the methods are inefficient, because a large part of the input energy is not used. Another disadvantage is the high space requirements of most facilities.
The furnaces can thus only be operated inefficiently, which further increases the production costs of the alloy material which is anyway more expensive compared with steel.
It would therefore be desirable and advantageous to obviate prior art shortcomings and to provide an improved furnace for thermal treatment of light metal components, and an improved method of operating the furnace capable of cost-effective and efficient mass production of light metal components.
According to one aspect of the present invention, a furnace for thermal treatment of light metal components which are continuously transported through the furnace, includes a heat source, a conveyor transporting the light metal components through the furnace in a transport direction, and a blower producing an airflow circulating inside the furnace. The airflow heats the light metal components inside the furnace by convection, and a light metal component entering the furnace and a light metal component exiting from the furnace are constructed as a barrier so as to hinder the airflow from escaping from the furnace.
According to another aspect of the invention, a furnace for thermal treatment of light metal components which are continuously transported through the furnace, includes a heat source, a conveyor transporting the light metal components through the furnace in a transport direction, a blower producing an airflow circulating inside the furnace, wherein the airflow heats the light metal components inside the furnace by convection, and partition walls arranged on the conveyor at mutual distances between the partition walls. At least one light metal component is arranged between two partition walls.
According to another aspect of the present invention, a method for thermal treatment of light metal components in a furnace, wherein the light metal components are continuously transported through the furnace, includes placing a plurality of consecutively arranged light metal components on a conveyor belt, transporting the light-metal components through the furnace, wherein an entrance opening at an entrance region of the furnace is sealed by a light-metal component passing through the entrance opening, generating a continuously circulating warm airflow and overflowing the light metal components in at least one temperature zone inside the furnace with the airflow to thermally treat the light-metal components, while the light metal components are continuously transported through the furnace, and discharging the heat-treated light metal components from the furnace at an exit of the furnace, wherein an exit opening at an exit region of the furnace is sealed by light metal component passing through the exit opening.
According to yet another aspect of the present invention, a method of operating a furnace for thermal treatment of light metal components, wherein the light metal components are continuously transported through the furnace on a conveyor belt, includes arranging on the conveyor belt partition walls separating mutually different temperature zones, placing at least one light-metal component on the conveyor belt between two partition walls, and transporting the at least one light-metal component through the furnace.
With the airflow circulating in the furnace, only the energy dissipated on the plate or the component or energy occurring as lost flows needs to be replenished, wherein the alloy components can be heated in the furnace by convection by the airflow and a respective light metal component entering the furnace and a respective light metal component exiting the furnace can act as a barrier and prevent the airflow from escaping from the furnace.
The furnace according to the invention uses convection for the thermal treatment, especially for heating the light metal alloy components. A light metal component within the context of the invention may be an already formed component, but also a component and an intermediate stage, or even a plate, which is transformed subsequent to the thermal treatment.
Advantageously, light metal components made of an aluminum alloy, in particular made of a wrought aluminum alloy, may be treated with the furnace according to the invention. The respective components may be placed on a clocked or continuously operating conveyor, and may then enter the furnace evenly spaced in single file, and preferably at regular intervals separated by additional pressure-seal baffles. The furnace is thus constructed at an entrance so that a light metal component entering the furnace and a light metal component exiting the furnace operate as a barrier, so that the airflow circulating within the furnace does not escape from the furnace. At each transition from a component located in the entrance region to the next component entering the entrance region, and likewise at the exit of the furnace, losses occur due to the separation between the individual components. In addition, overflow losses also occur at a gap between the component or barrier and the adjacent terminations. Because a number of components can be transported over a short distance through the furnace either in a clocked or continuous fashion, particularly short cycle times of a few seconds can be realized so that the furnace can effectively handle large quantities of light metal alloys for thermal treatment.
According to an advantageous feature of the present invention, the components to be heated may be transported continuously, without any interruption. Accordingly, components may be continuously placed onto the conveyor belt at the entrance of the furnace, transported through the furnace and again removed from the transporters at the exit of the furnace.
According to another advantageous feature of the present invention, the continuous transport may also cooperate with upstream and downstream production systems commensurate with the production cycle. For example, the conveyor belt may be briefly stopped each time a new component is added and then possibly also when at the same time a heated component is removed at the exit of the furnace and then restarted, until the next component.
According to another advantageous feature of the present invention, the transport speed of the components through the furnace may not only be selected as a function of the residence time of the components inside the furnace itself, but may also be adapted to the production process such that a sufficient quantity of heat-treated components is always provided for further processing.
Inside the furnace according to the invention, one or more heat sources may be arranged to generate at least a predetermined temperature. This temperature is advantageously a temperature between 100° C. and 600° C., which then produces with a circulation system, in particular an air circulation system arranged inside the furnace, in conjunction with a duct system formed in the furnace, an airflow passing over the light metal components transported through the furnace. The heated airflow then exchanges heat with the surface of the light metal components due to the forced convection, thus causing heat transfer from the airflow to light metal component. The furnace according to the invention uses hereby the high thermal conductivity of aluminum in conjunction with the large surface area relative to the mass of the light metal component, so that the lightweight metal component can be thermally treated, in particular heated, within a very short time.
An exit region is then formed at the exit of the furnace, wherein the light metal components exiting the furnace prevent the airflow from escaping from the furnace.
Both externally heated air as well as hot gas flows may be used for convection heating. Within the context of the present invention, the airflow may be any type of gas flow, for example also the flow of a reaction gas.
Overall, the furnace according to the invention offers the advantage that the entire system need not initially be heated at the startup of production, but only the air circulated in the furnace must be tempered accordingly. The furnace according to the invention can thus operate with an effective efficiency and with significantly lower energy costs compared to a heating system operating using radiation or induction. In particular, by circulating the airflow and by preventing the airflow from escaping, it is possible in conjunction with a thermal encapsulation of the furnace, to only slightly reheat the heated airflow with the heat source during circulation, thus significantly reducing the energy cost during the operation of the furnace according to the invention.
According to another advantageous feature of the present invention, the heat source may be designed as an electric heater and/or as a fuel-fired heater. The heat source may be arranged inside the furnace after and/or before the circulation system. The heated airflow or gas flow advantageously passes directly to the light metal components, so that no flow losses occur between the airflow heated directly by the heat source and a long duct system. After the airflow has passed over the light metal components, it may enter a duct system and be once more supplied to the circulating system, wherein it may then be reheated again to the desired temperature shortly before or after the circulating system by a heat source disposed therein.
The choice of heat source, i.e. whether electric heater or fuel-fired heater, depends in particular on the availability of energy, the energy costs and the size of the furnace according to the invention. For smaller lot sizes, it may be beneficial to use an electric heater. Within the context of the present invention, however, both types of heating systems may also be combined so that the furnace is modular and can be used for various purposes.
According to another advantageous feature of the present invention, the circulation systems may be arranged as a blower inside the furnace. Depending on the temperature to be generated, the blower may be arranged, for example, inside the duct system, or after the airflow has passed over the light metal components, so that the airflow or gas flow having an initial temperature reaching occasionally 600° C. has cooled down on the alloy components before passing the blowers. The blowers are thus not exposed to the maximum temperature of more than 400° C. or even of more than 500° C., but can be operated in a flow of warm air at about 100° C. to 400 C.
According to another advantageous feature of the present invention, the blowers may be used with different air blower settings, so that the airflow velocity or gas flow velocity, with which the air flows over the light metal components, is adjustable. This allows two adjustment parameters in conjunction with a temperature control, so that heating of the light metal components can be adjusted via the flow rate and/or the temperature of the air flow.
According to another advantageous feature of the present invention, the furnace may be thermally encapsulated, wherein sealing elements may advantageously be arranged at the entrance and/or exit of the furnace; the sealing elements may advantageously be formed as replaceable baffles. The thermal encapsulation is, for example, constructed as a thermally insulated jacket of the furnace, so that residual heat does not escape after passing the light metal components, or when passing through the duct system of the furnace.
Furthermore, particularly in the pulsed or continuous bulk transport of light metal components into the furnace and out of the furnace, the entrance and the exit region, i.e. the entrance and the exit, are therefore critical, since heat, but also the air flow, may be able to escape due to the convection principle of the furnace according to the invention. For this purpose, the entrance and the exit may each be formed such that successive light metal components which continuously enter and exit the furnace seal the entrance and/or exit such that a negligible quantity of the airflow circulating within the furnace escapes. Inevitably, hot air/gas exiting to the outside through gaps at the entrance and exit can be collected by way of overlapping hoods and returned to the circulation, thereby further increasing the efficiency.
By using the geometry of the components for the purpose of sealing to enhance the leak-tightness, sealing elements are formed on the entrance and/or the exit, wherein the sealing elements may advantageously be formed as a shaped baffle. When using different light metal components, especially different sized plates, the shaped baffles may be exchanged so that the cross-sectional area or the cross-frame area of the light metal components perpendicular to the transport direction spanning the shaped baffles may be constructed such that only a small gap is formed in a peripheral edge region. The furnace according to the invention can thus be optionally used for light metal components with different geometric dimensions.
According to another advantageous feature of the present invention, the furnace may advantageously have at least two temperature zones, wherein the light metal components may be used as a barrier between the zones, and more particularly, interchangeable shaped baffles may be located at a transition between the zones. According to another advantageous feature of the present invention, a first temperature zone and second temperature zone may thus be formed in a furnace having two different temperature zones, so that the light metal component crossing from one zone into another zone operates as a barrier of a transition, similar as at the entrance or the exit of the furnace. Again, changeable shaped baffles may be arranged here, so that an efficient air seal is formed between the zones even when the light metal components have different geometrical dimensions.
A mutually different thermal heat treatment may also be performed in the respective temperature zones by selecting the airflow speed and/or the air temperature. According to another advantageous feature of the present invention, two blowers may be arranged which generate, for example, mutually different flow velocities in the respective zone. Moreover, two heat sources for generating different temperatures may also be arranged inside the furnace. Within the context of the invention, the flow velocity within a respective zone may also be individually adjusted on the air nozzles associated with the zones via nozzles having an adjustable cross-section, so that only one blower is used. In the context of the invention, a temperature zone may also be configured as a cooling zone, so that in this case an airflow which is cold compared with the airflow into heat treatment zone having a temperature of, for example, 50° C. or even only 10° C. may flow around the light metal components.
Advantageously, the shaped baffles may have an opening corresponding substantially to a transverse frame area of the light metal components orthogonal to the transport direction. This ensures that even when a light metal plate is slightly slanted only small gaps are present when the plate passes through the shaped baffle, thereby preventing leakage of the air flow.
According to another advantageous feature of the present invention, the furnace may have a drying zone in the region of the entrance and/or a cooling zone in the region of the exit. In this way, a lubricant or other coating disposed on the light metal components can first dry in the drying zone or be removed from the light metal components. The light metal components may thereafter be thermally treated in the at least one temperature zone and then optionally cooled down again in a cooling option located at the exit of the furnace. The components may be cooled down to a component temperature of 100° C. or even 50° C., or also to room temperature. In this way, for example, thermal treatment, solution annealing, aging, or reverse annealing may be completed in a controlled manner.
According to another advantageous feature of the present invention, the circulating airflow inside the furnace may be passed across a surface of the light metal components, so that the airflow flows over the entire surface area of the light metal components. When the air flows over the components, heat is exchanged between the heated/cold air or hot gas and the comparatively colder or warmer light metal component. Advantageously, the airflow may pass continuously across the front side, but also across the rear side of the light metal component, so that both sides are evenly heated. The respective temperature set in the light metal component can then in turn be adjusted by selecting mutually different air temperatures or mutually different flow rates. For example, the parameters temperature and flow rate may be adjusted in only one temperature zone, so that different components can be thermally treated in the same furnace. When two or more temperature zones are present, the flow velocity and the temperature may also be adjusted individually in each zone.
Advantageously, the light metal components may be transported through the furnace on a conveyor belt, in particular a chain conveyor. In the context of the invention, the conveyor belt, in particular the chain conveyor, includes receptacles or seats with attachments in which the light metal components, which may be shaped as plates, can be stored with a substantial vertical orientation. In addition, the system then becomes more compact, so that the airflow passes across the components essentially in the vertical direction from the bottom to the top or from the top to the bottom. The transport direction then corresponds to a substantially horizontal direction, so that the vertically oriented components assume the respective flow guiding and sealing function between the zones and at the entrance and at the exit. The components may be arranged at an angle.
Advantageously, the light metal components themselves may be heated inside the furnace to a temperature between 200° C. and 450° C. Metallurgical processes then occur in the aluminum alloy used in each case, in particular wrought aluminum, which later produces good formability or a corresponding homogeneous microstructure with the desired strength properties.
The present invention also relates to a method for the thermal treatment of light metal components in a furnace, wherein the furnace has at least one of the aforementioned features and the method includes the following steps:
With the method according to the invention, consecutively arranged light metal components, such as also light metal plates, may be provided on a conveyor belt and continuously moved through a furnace. A hot air or gas flow may then be generated inside the furnace using a heat source and circulated with a blower, so that the hot air or gas flow flows across the light metal components. The light metal component itself is then heated by the forced convection on the surface of the light metal component, in particular on an upper surface as well as a lower surface of the light metal component, whereby the light metal component, in particular when using an aluminum alloy, can be heated in a very short time of sometimes only a few seconds due to its excellent thermal conductivity.
According to an advantageous feature of the present invention, the respective entrance or exit opening may be sealed by the respective light metal component passing through when the light metal component enters or exits the furnace, so that the air or gas flow generated inside the furnace barely escapes to the air surrounding the furnace. According to another advantageous feature of the present invention, two or three light metal components successively passing through the entrance opening may also assume a sealing function. The same applies to the exit opening.
Inside the furnace itself, the heating of the light metal component may be adjusted by selecting the flow rate of the air or gas flow and/or the air or gas temperature of the air or gas flow. Two, three or more temperature zones may be separated inside the furnace, wherein different heating effects can be performed on the light metal component via the parameters flow rate of the airflow or temperature of the air flow.
The heat-treated light metal components may be supplied within the context of the present invention to further processing, most advantageously with a cycle time of less than 15 seconds for each component.
According to another advantageous feature of the present invention, the furnace may include a drying zone and a cooling zone, wherein the light metal components passing the drying zone are dried in the drying zone; in particular a lubricant present on the light metal components is dried. Moreover, the light metal component may be cooled in a cooling zone to a cold-hardening temperature. Advantageously, a cooling zone may be arranged at the end of the furnace; however, one or more cooling zones may also be arranged between the individual temperature zones, allowing a heated component to be cooled and then reheated.
According to another advantageous feature of the present invention, the shaped baffles arranged in the furnace, in particular at the entrance and in the exit, but also at a transition between the zones, may be exchanged in a multi-zone furnace depending on the light metal components to be treated. The shaped baffles may advantageously be selected such that a cross-sectional frame area disposed transversely to the transport direction, in conjunction with the respective light metal component passing the shaped baffle or also with two or three passing light metal components, seals in an optimal manner, so that the airflow cannot escape.
The above-mentioned features may be combined with one another within the context of the invention in any manner with the associated features, without departing from the scope of the invention. The afore-described parameters can also be applied in any way to the embodiments described below.
In another embodiment, in a furnace for the thermal treatment of light metal components, wherein the light metal components can be transported continuously through the furnace and the furnace includes a heat source, an airflow may be circulated inside the furnace, wherein the light metal components can be heated inside the furnace by the airflow through convection and light metal components can be transported on a conveyor through the furnace, wherein spaced-apart partition walls are arranged on the conveyor and at least one light metal component may be arranged between two partition walls.
The aforementioned features relating, for example, to different temperature zones, the heat source itself, the flow velocity or the airflow temperature, but also the sealing elements in the form of shaped baffles can be combined with this embodiment without departing from the scope of the invention. A hybrid structure, wherein the light metal components are themselves arranged as a barrier in combination with partition walls placed on the conveyor, may be constructed, whereby the partition walls representing the larger light metal component are each heated in the furnace, while smaller light metal components or even complex shaped light metal components may be arranged between the partition walls, i.e. between the larger light metal components.
With this approach, light metal components having different dimensions may be placed between the two partition walls, wherein the outer geometry of the light metal components must be smaller than the outer dimensions of the partition walls, so that the partition walls assume a sealing function in a continuous transport process and the light metal components do not protrude over the partition walls.
Furthermore, two, three or four or more light metal components may be simultaneously arranged between two partition walls and heat-treated at the same time, wherein the light metal components may also have complex three-dimensional shapes.
When employing partition walls and placing at least one light metal component between two respective partition walls, the furnace may be used for different production runs, without requiring retrofitting. For example, light metal components having mutually different outside dimensions, particularly light metal plates, may be transported in direct succession through the furnace according to the invention, wherein in the sealing function is assumed by the partition walls and the plates can be simply inserted in receptacles arranged between the partition walls. In this way, the furnace according to the invention can be flexibly utilized, without requiring set-up times for the conversion of the furnace for a new production run. This saves acquisition and maintenance costs of the furnace according to the invention.
Furthermore, the furnace with partition walls has optionally at least two mutually different temperature zones, in which the components are heated to mutually different temperatures. For example, the component may initially be heated step-wise and/or cooled step-wise.
According to another advantageous feature of the present invention, the partition walls may be constructed to serve as a barrier, wherein a sealing function is achieved upon passing a partition wall of an entrance and/or an exit and/or a transition, so that the airflow is prevented from escaping from the furnace; in particular, two successive partition walls may form a continuous seal at the entrance and/or exit and/or the transition. Within the context of the invention, the transition is located between two temperature zones, so that the component transitions from one temperature zone to the other temperature zone.
Advantageously, a seal may be formed by two consecutive partition walls which are arranged substantially at an angle between preferably 10° and 85° with respect to the transport direction. The partition walls may advantageously be arranged such that, due to their angular position, the entrance and/or exit and/or the transition are substantially sealed by two partition walls, so that a respective airflow is prevented from escaping from the furnace, or from passing from one temperature zone into the other temperature zone.
According to another advantageous feature of the present invention, the partition walls may be arranged on the conveyor so that they can be exchanged. Within the context of the present invention, large partition walls of mutually different sizes may be arranged on the conveyer itself, or the distance between two partition walls may be varied. For example, the partition walls may be arranged on the conveyor with a greater spacing when heating two, three, four or more light metal components simultaneously, whereas when heating only a single light-metal component disposed between the two partition walls, the partition walls may be arranged with a mutual spacing that leaves only a small gap between the partition wall, the component and the next partition wall, thus allowing the airflow to flow across the light-metal component.
Within the context of the invention, the conveyor may be designed in particular as a chain conveyor or a conveyor belt. The conveyor can then be operated continuously, wherein in another preferred embodiment, the partition walls may be arranged on the chain conveyor before the entrance and be removed after the exit of the chain conveyor. In this way, a return of the chain conveyor requires only a small footprint, which would otherwise be significantly larger due to the partition walls protruding from the chain conveyor. Accordingly, a much smaller return cross-sectional area is required in relation to the cross-sectional area of the conveyor through the furnace, wherein respective partition walls are placed on the conveyor.
Furthermore, the airflow in the furnace may advantageously be guided by the partition walls themselves and, more particularly, two mutually different air flows in two mutually different temperature zones may be separated by a partition wall, wherein the air flows across the surface of the light metal components. Within the context of the invention, a respective airflow may thus be selectively utilized in a separate temperature zone due to the excellent thermal properties of the aluminum material, so that that the desired temperature of the light metal component can be specifically adjusted in the temperature zone by the airflow flowing across a light metal component.
Different temperature zones may be separated from one another by the partition walls, wherein the individual air flows are guided by the partition walls such that they substantially do not cross over into a different temperature zone. Within the context of the invention, the partition walls may advantageously be insulated, so that heat conduction from one temperature zone into the second temperature zone by the partition wall itself is minimized. Furthermore, within the context of the invention, the partition walls may advantageously be coated, so that the partition walls dissipate only a small amount of thermal energy from the air flowing across the partition walls. Advantageously, a thermally insulating coating may be employed.
According to another advantageous feature of the present invention, the partition walls may be arranged at an angle to the transport direction, for example at an angle between 10° and 80°, or between 20° and 70°, or at an angle between 30° and 60° and advantageously at an angle between 40° and 50°. Arranging two successive partition walls at an angle at an entrance and/or exit and/or, a transition advantageously ensures a continuous seal. As a second advantage, the angular arrangement also separates the air flows of mutually different temperature zones from each other.
Another aspect of the invention relates to a method of operating a furnace, wherein the furnace has a continuous conveyor for light metal components and at least two partition walls are arranged on the conveyor, wherein a respective light-metal component is positioned between the two partition walls and thereafter passes through the furnace, wherein furthermore mutually different temperature zones are separated by the partition walls. Within the context of the present invention, the interior of the furnace is thus sealed by the partition walls that continuously travel on the conveyor, wherein the light metal components arranged between the partition walls are thermally treated by an airflow circulating within the furnace.
For this purpose, two consecutively arranged partition walls seal the entrance region and/or the exit region and/or a transition region, wherein the airflow circulating in the furnace, in particular the airflow circulating in the respective temperature zone of the furnace, is hindered from escaping from the furnace or from crossing into a different temperature zone.
According to another aspect of the present invention, the light metal components can be transported continuously through the furnace and the furnace includes a heat source, is characterized in that an airflow can be circulated in the furnace, wherein the light metal components in the furnace can be heated by the airflow through convection and the light metal components can be transported through the furnace on a conveyor, wherein an entrance and/or an exit of the furnace is sealed by relatively movable barriers.
The relatively movable barriers are designed in particular as fast-opening and fast-closing barriers, wherein a relative movement of the barriers is preferably a translational movement. Consequently, a light metal component placed on the conveyor is transported toward the furnace, with the barrier opening just before the light metal component enters the furnace, whereafter the light metal component enters the furnace and the barrier closes again immediately after the light metal component has entered the furnace. With this embodiment, light metal components of different sizes can be transported through the furnace, regardless of their external dimensions.
The aforementioned features regarding the heat source, the blower and the adjustable temperatures and the mutually different temperature zones also apply to the third embodiment.
According to another advantageous feature of the present invention, a relatively movable barrier may be arranged between two different temperature zones. It is then conceivable within the context of the invention that three relatively movable barriers may be arranged at an entrance, in at least one transition between two different temperature zones and at an exit of the furnace according to the present invention, which briefly open and immediately close each time a light metal component passes. The barriers within the context of the present invention can be simultaneously controlled, wherein this embodiment is particularly advantageous for light metal components which are arranged on the conveyor at continuous intervals. All barriers then open simultaneously, so that in the embodiment with three barriers, three light metal components then enter a respective next space of the furnace, whereafter the barriers close again. This embodiment is advantageous, in particular, when the circulating airflow is turned off or decreased. Within the context of the invention, however, each barrier can also be operated individually, i.e. separately opened and closed. Separately opening and closing each barrier is particularly advantageous when light metal components are arranged discontinuously on the conveyor.
In the present invention, a relatively movable, in particular fast-opening barrier is advantageously formed as a sliding gate, wherein the barrier may be moved up or to one side in relation to the transport direction of the light metal components, wherein the barrier is moreover preferable constructed in two parts, so that each part of the barrier can be displaced to one side of the furnace. In particular, a long excursion when opening the barrier is eliminated with a two-part embodiment of the relatively movable barrier compared to a one-part barrier.
Even with aperture sizes of 1 m or more, by constructing the barrier in two parts, each barrier needs to be opened and then closed again in this case by only 0.5 m. This shortens the opening and closing times of the barrier especially with the two-part design.
Advantageously, an actuator is connected to the barrier for opening and closing the barrier wherein the actuator preferably performs a linear movement and can be driven pneumatically, hydraulically or electrically. An electromechanical actuator is also contemplated in the present invention. The actuator itself should be mechanically robust and have a simple design so as to be unaffected by thermal expansion caused by the thermal loads of the furnace, and an electronic control unit may optionally be arranged if possible in the marginal region or outside the furnace itself, so as to prevent defects due to the thermal loads.
According to another advantageous feature of the present invention, the furnace may be surrounded by a shell, wherein the barriers themselves are positioned in particular inside the shell or the barriers penetrate the shell and are movable in a slot extending through the shell for opening and closing. In the first embodiment, thermal energy is hindered from escaping through the slots for opening and closing the barrier in particular with barriers arranged in a transition region from one temperature zone into a second temperature zone located within the shell. However, this is only practical for smaller opening widths of the barriers in order to keep the outer dimensions of the shell also small. However, when an opening of the barrier of 1 m or more is necessary, it is advantageous within the context of the present invention, when the barriers can be moved through a respective slot of the shell. The barriers then leave at least partially the interior of the furnace upon opening and return into the furnace upon closing.
According to another advantageous feature of the present invention, heat loss through the slot may be reduced by providing thermal insulation measures in the slot region. For example, this may be a thermal seal. In another advantageous embodiment, the partition walls may themselves be coated and/or thermally insulated. In this way, the barrier itself can, on one hand, keep the heat input caused by the airflow flowing across the barrier small and, on the other hand, prevent the heat from exiting through the barrier by way of heat conduction at the entrance and/or exit, as well as prevent—by way of a thermally insulated barrier—heat transfer by thermal conduction from one temperature zone to the next temperature zone having a different temperature.
The invention also relates to a method for operating the furnace with relatively movable barriers, wherein a light metal component is placed on the conveyor and the light metal component is transported into the furnace, wherein the barrier is opened at the entrance of the furnace just before the light metal component enters the furnace and is closed again immediately after the lightweight metal component has entered the furnace and/or wherein the barrier at the exit of the furnace is opened just before the light metal component exits from the furnace and is closed again immediately after the light metal component has exited from the furnace.
Airflow recirculated within the furnace may advantageous be stopped or reduced when a barrier is opened, and may be restarted or increased after the barrier is closed. This ensures that the amount of heat escaping the furnace or the heat transfer between the mutually different temperature zones is reduced to a minimum when the barrier is opened or closed. The energy costs of operating the system are thereby reduced.
Moreover, within the context of the present invention two or more light metal components may pass the barrier when a barrier is opened, and when the barrier is closed again after the light metal components have passed the barrier. In this way, the furnace according to the invention and the method of operating the furnace can be flexibly used so that different production lines of metal components to be heated can be thermally treated with the furnace without long setup times. For example, light metal components having different external geometric dimensions, in the form of plates or even complex-shaped three-dimensional metal components may be simultaneously thermally treated in the same furnace without requiring a reconfiguration or modification of the furnace.
Within the context of the invention, the relatively movable barriers may advantageously be opened by a control system only as wide as necessary to create a sufficiently large unobstructed opening sufficiently for passage of the component according to its external geometric dimensions. The barrier(s) is/are then closed again after the component has passed. Thus, for example, an opening slightly larger than that 1 m2 may be provided for a large plate of 1 m2. For a plate having an area of only ¼ m2, the barrier may be opened only so far as to provide an opening slightly larger than ¼ m2, so that the plate can pass through the opening, whereafter the barrier is again closed.
Within the context of the invention, a barrier that opens in three directions may be selected, wherein the barrier is formed by two barriers moving toward each side of the conveyor and a barrier that is movable vertically upward relative to the conveyor, so that the respective unobstructed areas can be individually adjusted. This minimizes the energy exiting via the slots when the components pass into the furnace.
According to another advantageous feature of the present invention, the light metal components may be arranged an angle to the transport direction, in particular at an angle between 30° and 90°, allowing many components are to be transported successively and continuously through the furnace, wherein the furnace has longitudinal outside dimensions of maximally several meters, instead of several dozen or even several hundred meters which would otherwise be required when plates are placed on the conveyor horizontally, i.e. plates or light metal components having a lengthwise extension in the transport direction. The airflow can then be circulated within the furnace according to the invention from the bottom to the top or from the top to the bottom and flows across the plates arranged on the conveyor at an angle to the transport direction and optionally across the partition walls arranged in between. In summary, a universally usable furnace having compact overall dimensions for the heat treatment of light metal components with various geometrical dimensions can hereby be provided.
Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:
a and b shows relatively movable barriers in a furnace according to the invention.
Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.
Turning now to the drawing, and in particular to
Within the furnace 1, the light metal component 2 first comes into contact with a drying zone T in which the light metal component 2 is dried to remove a possible lubricant. An airflow L circulates within the drying zone T, which flows around both a front side 5 and a back side 6 of the light metal component 2. The light metal component 2 transitions from the drying zone T into a first temperature zone Z1, in which again an airflow L1 flows around the front side 5 and the back side 6 of the light metal component 2. The airflow L1 flowing around the light metal component 2 in the first temperature zone Z1 has hereby a flow velocity v1 and a temperature T1, thus subjecting the light metal component 2 to a predetermined component temperature within the temperature zone Z1.
Subsequently, the light-metal component 2 enters a second temperature zone Z2, in which again an airflow L2 flows across a front side 5 and a back side 6, wherein the airflow L2 of the second temperature zone Z2 has a second flow velocity v2 and a second temperature T2. In this way, a component temperature of the light metal component 2 is adjusted when passing through the second temperature zone T2.
After the second temperature zone T2, the light metal component 2 enters a cooling zone Z3, wherein in the cooling zone Z3 an airflow L3 again flows across the front side 5 and the rear side 6 of the light-metal component 2, which has a third flow velocity v3 and a third temperature T3, wherein in particular the temperature T3 is lower than the temperature T1 and T2, and the flow velocity v3 is higher than the flow velocities v1 and v2. The component is thereby cooled in the illustrated embodiment in the cooling zone Z3 to a cooling temperature. The component then exits from the furnace 1 at an exit A and is removed, and then supplied as heat-treated component 7 to additional unillustrated treatment processes.
The individual air flows L can be produced with an unillustrated blower, and the flow speed v1, v2, v3 can then be adapted to the respective zone by varying a cross-section or by using a valve. Within the context of the present invention, however, each zone may have a separate blower. The same applies to the temperature. The air may be heated by one or more heat sources, for example, a separate heat source may be associated with each temperature zone Z1, Z2.
In the embodiment shown in
The light metal component 2 according to
Furthermore,
A significant advantage of the present second embodiment according to
In the embodiment shown in
a and 10b show another embodiment of the relatively movable barriers 18, wherein the barriers 18 perform hereby the relative movement R by way of a slot 22 disposed in the shell 20.
While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2012 104 537.2 | May 2012 | DE | national |
