Refrigeration – Automatic control – Of external fluid or means
Reexamination Certificate
2000-02-18
2001-06-05
Walberg, Teresa (Department: 3742)
Refrigeration
Automatic control
Of external fluid or means
C165S294000
Reexamination Certificate
active
06240735
ABSTRACT:
TECHNICAL FIELD
This invention relates to the field of pneumatic flow dampers, and more particularly flow dampers for use in the field of refrigeration devices.
BACKGROUND ART
Refrigeration equipment for providing cold storage of articles, such as residential refrigerators for storing food items, include several different temperature zones, or compartments. Common among these are a freezer compartment for maintaining sub-freezing temperatures, and a fresh food compartment for maintaining a cool temperature for fruit and vegetable produce. The known method of regulating the different compartment temperatures is to use a compressor, evaporator, and fan to provide sub-freezing air to the freezer compartment, and to bleed some of this air to cool the fresh food compartment, as necessary, to maintain the fresh food temperature between freezing and room ambient.
There are several known prior art control methods and systems for achieving this. The least cost method is to use a manually operated damper in the bleed line and a thermostat in the fresh food compartment. The refrigerator user then adjusts the damper position and the thermostat set point temperature to selected values. The thermostat then actuates the refrigeration system (i.e. compressor and evaporator fan) to control the cool air flow to the freezer in response to the actual fresh food compartment temperature being above and below the thermostat set point. The freezer temperature then is dependent on the fresh food compartment set point temperature and the damper position. This has several drawbacks, including the instability of the freezer temperature, as well as longer operating cycle times of the compressor and evaporator fan. This results in higher operating costs due to the lower electrical efficiency of the refrigeration system.
A less common, but more expensive type control system used in “high performance” refrigerators (approximately 15% of to the refrigerators produced in the United States) is to use a freezer compartment thermostat to control actuation of the refrigeration system and to modulate the cool air flow to the fresh food compartment with a damper which is automatically positioned by a refrigerant charged bellows. The bellows expands and contracts in response to the fresh food compartment temperature, and positions the damper in a manner to maintain the fresh food compartment temperature within a user selected temperature range. This provides direct control of the freezer temperature, and since the bellows temperature characteristics are predictable, this system provides more accurate temperature control of both compartments.
Despite the improved efficiency of the more expensive system, the controlled temperature of both compartments still varies over a substantial range of temperatures. This is due to the passive nature of both of these control functions, which is characterized by greater operating tolerances as well as limited response time. Alternatively, the growing use of microcontroller and microprocessor based controls in residential appliances now makes them cost effective for use in residential refrigerators. They provide increased control accuracy, faster response, and lower refrigeration cycle times, all of which result in higher efficiency and lower operating costs to the consumer.
Within these electronic control type systems, however, there remains the need for mechanical damper assemblies. To further improve the operating efficiency of the electronic controls these mechanical damper assemblies must preferably be capable of operating in a gated manner; i.e. in an open/closed sequence at a given duty cycle, as determined by the electronic control. The ideal damper assembly therefore must itself be capable of fast response as well as efficient air flow characteristics.
DISCLOSURE OF INVENTION
One object of the present invention is to provide an improved efficiency damper assembly. A further object of the present invention is to provide a mechanical damper assembly capable of gated operation between a full open and a full closed position. A still further object of the present invention is to provide a mechanical damper assembly capable of faster response times in achieving a commanded position.
According to the present invention, a damper assembly for controlling the flow of a fluid includes concentric inner and outer hollow cylinders, the inner cylinder being adapted to receive the fluid flow and to be nested within the outer cylinder in a manner which permits relative axial rotation of the cylinders about a common longitudinal axis, each cylinder having a side wall aperture for providing a fluid flow path therethrough, whereby the flow of fluid through the assembly is proportional to the degree of alignment of the cylinder apertures. In further accord with the present invention, the outer surface of the inner cylinder side wall includes fluid sealing members disposed thereon which restrict the fluid flow path through the assembly to the side wall apertures. In still further accord with the present invention the fluid sealing members are disposed circumferentially along each longitudinal end of the inner cylinder. In still further accord with the present invention, fluid sealing members are disposed longitudinally along the inner cylinder, at least one on each side of the inner cylinder side wall aperture.
In yet still further accord with the present invention, the damper assembly includes a source of rotational motive power which is adapted to engage with and rotate the inner cylinder relative to the outer cylinder, the source of motive power being selectably actuated to rotate the inner cylinder to establish a degree of registration of the apertures as necessary to provide a desired amount of fluid flow through the assembly. In yet still further accord with the present invention the outer cylinder is stationary relative to axial rotation of the inner cylinder. In yet still further accord with the present invention, the damper assembly includes a position control device which de-actuates the source of motive power in response to the rotational position of the inner cylinder at one or more selected locations corresponding to a desired relative positioning of the side wall apertures. In still further accord with the present invention, the source of motive power provides full slew axial rotation of the inner cylinder between a full flow position corresponding to substantial registration of the cylinder side wall apertures, and a minimum flow position corresponding to no overlap of any portion of the apertures.
The rotary damper assembly of the present invention provides high efficiency modulation of fluid flow through the assembly and is highly suitable for use with different electronic flow control applications, including refrigeration equipment. This efficiency is achieved through the dual cylinder configuration which provides slew rates which are compatible with gated operation as well as good fluid seal characteristics in the full closed position.
These and other objects, features, and advantages of the present invention will become more apparent in light of the following detailed description of a best mode embodiment thereof, as illustrated in the accompanying Drawing.
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Kolson John A.
Lanz Douglas C.
Starenchak Robert W.
Chiantera Dominic J.
Moore & Van Allen PLLC
Robertshaw Controls Company
Robinson Daniel
Walberg Teresa
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