The present invention relates to manufacturing ovens and methods of baking workpieces, and more particularly, to an oven presenting, and a method of baking workpieces utilizing, dimensions suitable for transverse baking, and/or a more uniform heating configuration having dual heat sources.
Manufacturing ovens are used to bake workpieces to specified temperature ranges as part of many curing processes. In automotive settings, for example, recently painted workpieces have long been conveyed longitudinally into an elongated oven that typically features radiant heat sources located along the outside perimeter of a chamber. Though widely utilized, various concerns are appreciated in the art. For example, the longitudinal orientation of conventional ovens works well for heating most vehicle body types but does not make efficient use of floor space. Where space is limited, some conventional ovens present a “U”-shaped layout that requires large spaces between workpieces, so as to provide necessary clearance when a longitudinal workpiece is processed through the turn of the oven.
Of further concern is often the method of heating. For example, it is appreciated by those of ordinary skill in the art that radiant heat transfers heat at high rates but only to the areas of the workpiece exposed through a direct line of sight. Convection heat is able to treat indirectly, but requires high volumes of air for good heat transfer rates. Irrespective of the mode of heating, however, another concern is the radial positioning of heat sources, which often results in inadequate heating of the workpieces near the lateral centerline of the oven. Moreover, conventional one-size fits all configurations do not enable the flexibility needed to focus heat where most needed. For example, with respect to vehicles, an area of particular concern is the lower heavy metal area between the wheel openings, known as the “rocker.” It is appreciated that this area requires greater heat saturation due to increased material thickness.
In the present invention, a more compact manufacturing oven layout is provided that facilitates transverse baking and addresses the afore-mentioned concerns. More particularly, in a preferred embodiment, the dimensions of the oven are such that the longitudinal axis of the workpiece is able to define an angle up to ninety degrees with the longitudinal axis of the oven (during baking), without substantially increasing the overall width of the oven. This layout may reduce operating costs, and required floor space and/or capital costs.
The inventive oven utilizes a combination of radiant and convection heating to treat the workpieces more effectively. Sufficient heating along the lateral centerline of the oven is provided, in one embodiment, by providing radiant heat from a high emissivity false floor, heated fresh air supplied through openings defined by the floor or by duct above the floor, and at least one ceiling fan for continued convection heating. Thus, among other things, the invention is useful for providing more uniform heating and treatment of troublesome areas, than do conventional ovens.
Thus, a first aspect of the invention concerns a transverse oven adapted for baking a workpiece, wherein the workpiece presents a first longitudinal axis, length and width. The oven includes an enclosable chamber defining an interior space, entrance and outlet openings, and a second longitudinal axis. The chamber, entrance and outlet are cooperatively configured such that the workpiece is able to enter, pass through, and exit the space, when the first and second axes define an angle greater than zero and up to ninety degrees. Finally, a plurality of radiant and convection heat sources are thermally coupled to the space and cooperatively configured to heat the entire workpiece to a target temperature range, when the workpiece is in the space.
A second aspect of the invention concerns a method of baking a workpiece defining a first longitudinal axis, in an oven defining a second longitudinal axis. The method preferably includes the initial step of rotating the workpiece to a transverse orientation, wherein the first and second longitudinal axes form a minimum angle, and entering the workpiece into the oven in the transverse orientation. Next, the workpiece is treated with convection and radiant heating during Bring-up, Equalize, and Hold periods, so as to cause the workpiece to reach a target temperature range. The workpiece exits from the oven in the transverse orientation, after the periods, and rotates back to the longitudinal orientation to continue the work-in-progress.
It will be appreciated and understood that the oven and methods of baking offered by the present invention provide a number of improvements and advantages over the prior art. The aforementioned aspects, features, and/or species of the present invention are discussed in greater detail in the section below titled DESCRIPTION OF THE PREFERRED EMBODIMENT(S).
Preferred embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein:
Referring collectively to
The inventive oven 10 is preferably used in conjunction with a conveyance system 14 suitable for conveying the workpieces 12 so that they enter, pass through, and exit the oven 10 at a controlled rate (
The oven 10 includes a chamber 22 defining a preferably enclosable interior space 24, an entrance 26, a longitudinal length, and an exit 28 (
The inventive oven 10 includes dual convection and radiant heat sources 30,32 that are each thermally coupled to the interior space of the chamber 22 (
In a preferred embodiment, the chamber 22 includes a false floor 34 above which the workpiece 12 travels as it passes through (
In another aspect of the invention, the false floor 34 functions to provide a uniform radiant heat source 32 and as such, is preferably formed of a “high emissivity” or thermally conductive material, such as uncoated steel, coated steel, steel alloys, and the like. Moreover, composite structures of plural layers of like or dissimilar materials may also be used. The remaining structures of the chamber 22 are also formed of material able to withstand the repeated application of anticipated temperatures (e.g., 350° F. for E-coat, and 250° F. for Prime and Top coat, etc.).
To heat the floor 34, at least one element 36 operable to generate radiant heat energy is positioned beneath, and proximate to the bottom surface of the floor 34 (
In a preferred embodiment, the oven 10 further includes at least one and more preferably a plurality of low emissivity reflectors 38 opposite the floor 34 and beneath the elements 36 (
In the illustrated embodiments, the elements 36 present congruently spaced radiant tubes 40 and a gas fired burner 40a (
As shown in
Consistent with the “U”-shaped configuration shown in
Also shown in the illustrated embodiment, the convection heat energy source 30 preferably includes a fresh air heater 42 fluidly coupled to an ambient space and the interior space 24 by at least one conduit 44 and more preferably, a plurality of conduits 44 (
The floor 34 presents a generally integral structure (
The preferred oven 10 further includes an exhaust system 50 fluidly coupled to and configured to cause heated air to flow from the interior space 24 and to an abatement system (not shown) in order to collect evaporated paint solvents and/or particulate matter released during the curing process. The exhaust system 50 includes at least one, and more preferably a plurality of outlet registers 52 preferably located at the upper corners of the space 24 (
In a preferred embodiment, the oven 10 yet further includes at least one, and more preferably a plurality of ceiling fans 58 located and configured to agitate the air within the space 24, so as to accelerate heating (
Finally, it is appreciated that the controller 16 is communicatively coupled to the sources 30,32 (including the fans 58). The preferred controller 16 is programmably configured to actuate the sources 30,32 for a predetermined period, or where sensory input is provided, until the occurrence of an event (e.g., a thermometer reading within the target temperature range). The controller 16 preferably provides a user interface so that information relating to workpiece condition and/or application may be entered by the operator and considered, as previously described. It is appreciated that suitable software, processing, storage and communicative capabilities of the controller 16 are readily determinable by one of ordinary skill in the art without undue experimentation, and as such will not be further described herein.
An exemplary method of baking a workpiece 12 utilizing the inventive oven 10 is therefore presented, and begins by rotating the workpiece 12 to a transverse orientation, just before entering the chamber 22. During an initial “Bring-up” period, the radiant floor 34, fresh air heater 42 and/or at least one ceiling fan 58 are actuated depending upon the application. For example, for proper curing of an E-coat layer, all of the components are preferably actuated; and for a Prime or Top coat, only the heater 42 and floor 34 are preferably actuated (so as to prevent anomalies caused by agitation in the finished product), during a 10-minute Bring-up period. In this example, for each of these applications, all of the components are preferably actuated for an additional 3 to 5-minute “Equalize” period, immediately following the Bring-up period; and finally, all of the components are again preferably actuated for a 20-minute “Hold” period, immediately following the Equalize period. The Bring-up, Equalize and Hold periods are determined after predetermining the target temperature range based on at least one condition of the workpiece. The uniformly baked workpiece 12 is then exited from the oven in the transverse orientation, and preferably rotated back to the longitudinal orientation to resume travel.
More preferably, the oven 10 defines multiple zones for concurrently treating a plurality workpieces 12. For example, the preferred oven 10 may be longitudinally configured to define Bring-up, Equalize, and Hold zones sequentially. In
The preferred forms of the invention described above are to be used as illustration only, and should not be utilized in a limiting sense in interpreting the scope of the general inventive concept. Obvious modifications to the exemplary embodiments and methods of operation, as set forth herein, could be readily made by those skilled in the art without departing from the spirit of the present invention. The inventors hereby state their intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of the present invention as pertains to any system or method not materially departing from but outside the literal scope of the invention as set forth in the following claims.
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Number | Date | Country | |
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20100038353 A1 | Feb 2010 | US |