Patent Application
20130167396
This disclosure relates to the field of heating, curing and drying systems, and in particular to heating, curing and drying systems where air is flowed from the ceiling or an end wall and past the object to be heated, dried or cured. More specifically, this disclosure relates to increasing airflow rates around an object.
This disclosure provides a system for heating, drying or curing an object, the system comprising a housing having a first wall and at least one second wall adjacent the first wall. The first wall and at least one second wall define an interior for holding an object to be heated, dried or cured. The system also includes an air plenum adjacent to, covering and disposed inward from the first wall, and at least one air plenum opening in the air plenum to supply air into the interior. A fan is disposed in the one air plenum opening. The system also includes a ductwork assembly adjacent to, covering and disposed inward from the second wall. The ductwork assembly is in air-communication with the air plenum, and has a ductwork opening so that substantially all air circulation in the interior is between the air plenum opening and the ductwork opening.
Before one embodiment of the disclosure is explained in detail, it is to be understood that the disclosure is not limited in its application to the details of the construction and the arrangements of components set forth in the following description or illustrated in the drawings. The disclosure is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. Use of “including” and “comprising” and variations thereof as used herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Use of “consisting of” and variations thereof as used herein is meant to encompass only the items listed thereafter and equivalents thereof. Further, it is to be understood that such terms as “forward”, “rearward”, “left”, “right”, “upward” and “downward”, etc., are words of convenience and are not to be construed as limiting terms.
As shown in the drawings, disclosed is a system 10 for heating, drying or curing an object or part (not shown) made of metal, wood, plastic, or some other material. For example, the system 10 can be used for object preheating, for paint drying, thermal degreasing, or for powder paint curing. The system 10 includes a housing 14 having a first wall 18 and at least one second wall 22 adjacent the first wall 18, the first wall 18 and at least one second wall 22 defining an interior 26 for holding an object to be heated, dried or cured. Wall as used herein refers to any housing planar surface, whether a ceiling, a floor, an end, or a side. More specific references include more specific wording.
More particularly, the first wall is a ceiling 18, and the second wall is a side wall 22. Still more particularly, there is a door 30 (see
The system 10 also includes an air plenum 42 (see
As illustrated in
The fan 50 increases the air flows within the interior 26 in the vicinity of an object (not shown) to increase curing rates, for example, associated with a spray application on the object, or to enhance air flow over the object during a heating, drying or a cure cycle. The variable speed control of the fan 50 permits various amounts of airflow around the object. For example, when a powder coat is just beginning to gel, it may be advantageous to have limited airflow around the object. After the powder begins to gel, and becomes firmer, the fan speed can be increased, increasing the amount of airflow past the gel. This reduces the gel curing time.
The system 10 further includes a return plenum or ductwork assembly 62 adjacent to, covering and disposed inward from a second wall or side wall 22, the ductwork assembly 62 being in air-communication with the air plenum 42, and having a ductwork opening 66 so that substantially all air circulation in the housing interior 26 is between the air plenum openings 46 and the ductwork opening 66. In other less preferred embodiments, the second wall can be a ceiling, a floor, or an end wall. Opening as used herein means any opening permitting airflow from the ductwork assembly or air plenum into the oven interior. In the disclosed embodiment, as illustrated in
As illustrated in
A heat source, such as an electric heater (not shown) or a gas heater 90 is disposed within the air plenum 42 in the housing side wall 34, and serves to heat the air and allow the system 10 to act as an industrial oven. In such instances, all walls and the air plenum and ductwork assembly are made from metal, in order to be compatible with the heated air. The system 10 further includes an oven exhaust 94 (see
The disclosed system 10 significantly increases the curing efficiency of a conventional industrial oven used to cure powder coating on metal, wood, plastic and other substrates. The system allows for low airflow during the gel period of powder coating, and then progressively increases the airflow, through the bake cycle, to allow for a nearly perfect cure.
The system 10 also aids in the drying of a product after the aqueous washing of a product. The system significantly increases the amount of air and turbulence delivered to the product. This increases the drying efficiency. In an instance where the system is used as a preheat oven, the system allows for a more uniform product temperature profile as the heat up rates for the different thicknesses are enhanced.
The system 10, in the preferred embodiment, is designed with variable frequency drives to allow the operator to pick a recipe, thus reducing the airflow thru the gel cycle. This allows the powder paint to set, prior to the full cure and required “Time at temperature” process parameters.
The system 10 is supplied with return plenums on each side and the roof of the chamber. These plenums are designed to capture the conventional heat losses through the walls and roof. This significantly increases the temperature uniformity within the oven chamber as the interior now includes a “Hot Wall” in lieu of the conventional “Cold Wall”. The system, including the fan layout and type, allows for a much greater amount of air delivered to a product as compared to a conventional oven. This increased airflow significantly increases the uniformity and heat transfer to the process and the customer's product. The system, by design, does not have ductwork on the positive side of the fan. As a result of this feature, the chamber is completely free of ductwork on the floor, thus allowing for the cleaning of the equipment, to be more efficient.
The oven control system, when programmable logic controller based, is designed to allow the operator to pick a recipe to provide the “optimum” process schedule. This a custom program with data acquisition to provide constant feed back of the oven performance. Additionally, through an operator interface, the operator can set the temperature, low flow, high flow, cycle times and process parameters.
Conventional systems having forced air ducts with circulating fans cause significant pressure drops across the air circulation system. This results in the need for higher horsepower fans, and increases in the cost of operating the system. In the system 10, substantially less horsepower is needed to circulate the same or even a greater amount of air, so improvements in energy efficiency of at least 50 percent over conventional systems is possible.
Various other features of this disclosure are set forth in the following claims.
