Refrigeration – Automatic control – Of external fluid or means
Reexamination Certificate
2003-05-30
2004-08-03
Norman, Marc (Department: 3744)
Refrigeration
Automatic control
Of external fluid or means
C062S150000
Reexamination Certificate
active
06769263
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to a baffle assembly in an air control device for a refrigerator, and more particularly to an improved baffle assembly having a deicing mechanism.
BACKGROUND OF THE INVENTION
In conventional dual-compartment refrigerators, a single evaporator fan introduces chilled air into the freezer compartment by blowing air across the evaporator coils of the refrigeration unit. Chilled air is introduced into the fresh food compartment through one or more air passages in a divider wall between the two compartments. An air control device is located within one or more of the air passages to control the flow of chilled air into the fresh food compartment.
Air control devices typically employ a baffle assembly having a fixed plate and a movable plate which can slide longitudinally relative to the fixed plate between two distinct positions. In a first or open position, a plurality of apertures contained in each plate are aligned, such that chilled air is allowed to flow through apertures and into the fresh food compartment. In a second, or closed position the plurality of apertures are unaligned and blocked, such that the baffle assembly prevents chilled air from flowing into the fresh food compartment when in the closed position.
Some baffle assemblies are constructed with the movable plate connected to one end of an armature and the fixed plate attached to a frame holding two solenoid coils positioned next to each other. The armature is located radially inside the cavities of the solenoid coils. Activation of one of the solenoid coils causes the armature to slide within the solenoid coils' cavities, causing the movable plate to slide longitudinally relative to the fixed plate. The direction of the armature's movements is dependent upon which of the solenoid coils is activated. Alternatively, the armature can be located radially inside the cavity of a single solenoid coil, where opposite electrical charges applied to the solenoid coil cause the armature to move in opposite directions within the solenoid coil's cavity.
In a refrigerator employing one or more air control devices with baffle assemblies as described above, one or more temperature sensors are positioned in various locations of the refrigerator. Each sensor is electrically connected to an air control device. If the baffle assembly is in the closed position and a sensor in the fresh food compartment detects an air temperature at or above a preset level, the sensor sends an electric signal to the baffle assembly to activate one of the solenoid coils, causing the armature to slide the movable plate relative to the fixed plate. As a result, the apertures in the two plates are aligned, thereby allowing chilled air to flow into the fresh food compartment. Likewise, when the baffle assembly is in the open position and the sensor detects an air temperature in the fresh compartment at or below a preset level, an electric signal is sent to the baffle assembly to activate the other solenoid coil, causing the movable plate to slide in the opposite direction. As a result, the apertures become unaligned and blocked, stopping the flow of chilled air to the fresh food compartment.
In order to minimize the amount of time that the solenoid coils remain energized, the system may have a further feature wherein the solenoid coils are deactivated when the temperature sensor detects a change in temperature after initial activation. For example, after the temperature sensor indicates that the air temperature in the fresh food compartment is above the pre-set maximum and the solenoid coil is energized to place the baffle assembly into the opened position, the solenoid coil will remains energized until the temperature sensor detects that the air temperature has stopped increasing. This indicates that the baffle assembly has in fact opened and that chilled air is flowing into the fresh food compartment. The baffle assembly then remains in the opened position after the solenoid coil has been deactivated.
In a conventional refrigerator, moisture at room temperature enters the fresh food compartment when the door of the fresh food compartment is opened. Moisture can accumulate throughout the fresh food compartment, including on the baffle assembly. When chilled air from the freezer compartment subsequently flows through the baffle assembly, the accumulated moisture may freeze, causing ice to form and immobilize the movable plate of the baffle assembly. Consequently, the baffle assembly becomes frozen, making it impossible to regulate the temperature of the fresh food compartment.
The prior art methods for preventing or removing ice on a baffle assembly are expensive and lead to high energy usage. In addition, some of the methods contribute to the premature failure of the solenoid coil. In particular, the currently preferred method uses a solenoid bobbin wherein the cavity created by the solenoid coil has an inside diameter that is larger than the outside diameter of the armature used to slide the movable plate. When the movable plate is idle, ice accumulates between the movable and fixed plates. Upon activation of the solenoid, the accumulated ice initially prevents movement of the plate. However, loose fit of the armature within the solenoid coil allows the armature to move up and down or side-to-side, ultimately breaking the accumulated ice. This additional movement causes added stress to be placed upon the coil while energized, which can lead to premature failure of the coil.
The problem is exacerbated because heat, generated as a natural by-product of energizing solenoid coils, becomes trapped within the solenoid coils. Since the plates are typically not made of a heat-conductive material, the heat does not migrate away from the solenoid coils and instead builds up within the coils. In the prior art described above, the solenoid coils are energized for a longer period because of the need to break free of the ice. The build up of excessive heat is one cause of premature failure of the solenoid coils.
In another prior art method, the solenoid coil periodically and momentarily reverses the direction of the movable plate to prevent the accumulation of ice. Specifically, when the temperature of the fresh food compartment rises above a preset level, the solenoid coil is activated to slide the movable plate to the open position. Once the temperature sensor detects that the temperature has stopped rising, the solenoid coil is deactivated. While in the open position, the solenoid coil is periodically activated to momentarily slide the movable plate into the closed position then immediately returned to the open position to prevent ice from accumulating. Likewise, when the baffle assembly is in the closed position, the solenoid coil is periodically activated to momentarily slide the movable plate into the open position, and then immediately back into the closed position. This method creates unnecessary energy consumption and adds a stress on the solenoid coil as a result of being regularly energized, leading to premature failure of the coils.
In another method, the armature used to slide the movable plate is substantially smaller than the cavity produced by the solenoid coil such that the armature rests within the solenoid coil at an angle. The movable plate rests on top of studs located on the top surface of the fixed plate. Because of the space between the plates created by the studs, any accumulation of ice results in a weak bond. The solenoid coil is periodically energized so that the movable plate maintains its current position and does not slide into another position. When the solenoid coil is energized, the magnetic field generated around the circumference of the angled armature causes the armature to straighten within the solenoid coil. As the angled armature straightens, the movable plate moves outward and away from the fixed plate, thereby breaking the weak ice bonds that had formed between the movable plate and the fixed plate. This method uses an additional amount of energy because the
Armour John
Nguyen Minh
Armour Magnetic Components, Inc.
Jenner & Block LLP
Norman Marc
LandOfFree
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