Drying and gas or vapor contact with solids – Apparatus – Houses – kilns – and containers
Reexamination Certificate
2000-03-14
2001-12-18
Wilson, Gregory (Department: 3749)
Drying and gas or vapor contact with solids
Apparatus
Houses, kilns, and containers
C034S174000, C432S250000
Reexamination Certificate
active
06330754
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention pertains to agricultural equipment, and more particular to apparatus for drying seed.
DESCRIPTION OF THE PRIOR ART
A vital step in processing some agricultural seed is drying the seed. Especially with corn, it is imperative that the kernels contain no more than a predetermined amount of moisture. Since ear corn as harvested almost always contains more moisture than is acceptable for storage and germination, it is necessary to artificially dry the corn. For that purpose, large ear corn dryers have been developed and are in widespread use.
A popular type of ear corn dryer is the single-pass reversing dryer. A typical single-pass reversing ear corn dryer is a large enclosure that can reach 25 or more feet in height. An enclosure length of approximately 50 feet and a width of approximately 25 feet are typical. A perforated floor extends between the enclosure walls several feet above and at an angle to the enclosure bottom floor. At the lower end of the perforated floor adjacent a back wall is an unloading door. A fill door is in the enclosure roof over the upper end of the perforated floor. The ear corn to be dried is loaded onto the perforated floor through the fill door. There is also an access door to the enclosure. The access door enables a person to walk into the enclosure for inspection and maintenance purposes.
A plenum is built on the outside of one of the enclosure walls. The plenum connects with the enclosure through a top opening in the enclosure wall above the perforated floor. The plenum also connects to the enclosure through a bottom opening below the perforated floor. The bottom opening is selectively closeable by a diverter door.
A blower connected to the plenum utilizes atmospheric air to produce drying air under pressure in the plenum. The diverter door is used to direct the flow of the drying air from the plenum to the enclosure. If the diverter door is in a first position, the drying air flows through the enclosure bottom opening into the enclosure. With the access door closed, the drying air flows upwardly through the perforated floor, through the ear corn loaded on the perforated floor, and out the fill door in the enclosure roof. Typically, the blower produces an air pressure inside the enclosure of between approximately three inches and five inches of water.
In a reverse drying process, the diverter door is in a second position. The atmospheric drying air then enters the enclosure through the top opening between the plenum and the enclosure. The fill door is closed, but the access door is opened. The drying air flows downwardly through the ear corn loaded on the perforated floor and then flows out the access door.
Ear corn dryers as generally described have been in use for many years, and they give generally satisfactory performance. An exemplary ear corn dryer is manufactured by KC Manufacturing, Inc. of Columbus, Wis. However, a potential problem with the prior ear corn dryers concerns the access door. As mentioned, the access door is closed when the atmospheric drying air flows from the plenum into the enclosure through the bottom opening and out the fill door. The pressurized drying air in the enclosure exerts a considerable force on the access door. For example, for a door four feet wide and eight feet high and an air pressure of three inches of water inside the ear corn dryer, the force on the closed access door was approximately 500 pounds.
To prevent the prior access door from flying open when released from the outside by a person who must enter the operating ear corn dryer, the access door was designed to open only inwardly into the dryer. However, the force holding the access door closed was too large for the person to overcome. Therefore, the dryer had to be shut down in order for the person to open the access door and enter the dryer. Once inside the dryer, the person was trapped while the dryer was operating. After completing his inspection or other work inside the operating dryer, it had to again be shut down so the person could open the access door and leave the dryer. The dryer shut downs and restarts to accommodate inspections and other work resulted in unproductive down time.
A related situation occurred in the reverse drying operation when the drying air flowed out the access door. The access door had to be reliably held open. If the access door became free to close unintentionally, it would slam shut with a great speed and force. If a person was in the way, injury could result.
To solve the problems associated with the prior access doors, it is known to build air locks over them. The air locks help to equalize the forces on both sides of the access doors for safer entry into and exit from the enclosures by operating personnel. With an air lock, the access door can be narrower than a normal door. Although generally satisfactory, the air lock design is undesirably expensive.
Thus, a need exists for an improved way to enter and leave an operating ear corn dryer.
SUMMARY OF THE INVENTION
In accordance with the present invention, a door is provided that permits safer entry into and exit from a pressurized enclosure than was previously possible. This is accomplished by designing the door to swing about an axis that is at approximately the midpoint of opposed edges of the door.
According to one aspect of the invention, the door swings about a vertical axis. For that purpose, the door includes two concentric pins, one each in a top edge and a bottom edge of the door. The pins are approximately midway between the door vertical edges. The door is thus divided into first and second panels, one on each side of a vertical axis of rotation through the pins. The pins are rotatable within a door casing in a wall of the pressurized enclosure.
The door swings between open and closed positions. When in the closed position, the door completely closes the casing in the enclosure wall. A first face of the door is then toward the outside of the enclosure, and a second face is toward the inside of the enclosure. When the door is closed, it is sealed against the door casing. When the door is open, the door first panel swings inside the enclosure, and the second panel swings outside the enclosure.
If the pins are midway between the door vertical edges, the forces on the two door panels are equal when the door is closed and the enclosure is pressurized. In that situation, the equal forces create equal and opposite torques about the door axis of rotation. Only a small external force, such as a person pushing lightly on the first panel from outside the enclosure, is needed to open the door. The person can safely enter the enclosure, and close the door behind him without danger of the door slamming shut. When the person wants to leave the enclosure, he merely either pushes lightly on the door second panel or pulls the door first panel. The door again swings easily open.
Because a door with equal area first and second panels has equal forces applied to it by the pressurized air, the door may flutter when closed. To assure that the door remains closed when the enclosure is pressurized, the door first panel is made with a larger area than the second panel. To do so, the door pins are located slightly closer to the vertical edge of the door second panel than to the vertical edge of the first panel. Consequently, the force on the door first panel from the pressurized air is greater than the force on the second panel. The door is thus held closed by a small net torque about the axis of rotation. Accordingly, a small but intentional manual effort is required to open the door.
It is a feature of the invention that the door is not limited to swinging about a vertical axis. The door is equally useful for swinging about a horizontal axis in a roof of a pressurized enclosure.
The method and apparatus of the invention, using a door with equal or approximately equal forces on both sides of an axis of rotation about which the door swings, thus provides easy and safe entry into and exit from a pressurized enclosure. The probability of inju
Cayen Donald
KC Manufacturing Inc.
Wilson Gregory
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