Automatic temperature and humidity regulation – Humidity control
Reexamination Certificate
1999-02-02
2002-05-21
Wayner, William (Department: 3752)
Automatic temperature and humidity regulation
Humidity control
C034S210000, C062S078000, C236S051000
Reexamination Certificate
active
06390378
ABSTRACT:
FIELD OF INVENTION
The present invention generally relates to a humidification system and methods in conjunction with other environmental control systems for maintaining and controlling the humidity content in perishable goods containers during transport and holding. This invention further relates to a portable centralized master unit container for performing the humidification operations in one or more portable perishable goods containers.
BACKGROUND OF THE INVENTION
It is generally well understood and widely accepted that it is desirable to prevent deterioration of the quality, quantity and appearance of consumable perishable goods, such as fresh fruits, vegetables, cheeses, meats, fish and the like, during lengthy transportation and holding operations, up to their final arrival in the global market.
Moreover, some foodstuffs, such as fruits and vegetables (e.g., broccoli) that must be shipped long distances to market (e.g., from Asia to North America) are shipped packed in crushed ice in the shipping container. As a consequence, less foodstuffs can be placed in the container because the crushed ice takes up part of the weight limit and available space in the container. The ice has been used not only for refrigeration, but also for humidification. Replacement of the crushed ice with a suitable system for a refrigerated and humidified atmospheric control allows for a significant increase (e.g., 30% to 50%) in the amount of foodstuffs that can be shipped in a container.
Preservation of moisture in perishable goods is a critical aspect of prevention of deterioration of perishable goods. Coyle et al. in U.S. Pat. No. 3,694,925 recognized this and understood that the actual process of refrigeration of perishable goods in railroad cars reduces the moisture content in the atmosphere around the goods, and within the goods, to an undesirable level. The solution proposed by Coyle et al. was to convey a portion of the condensed water from refrigeration to the intake of the circulating fan, while draining off the remainder of the water. This approach obviously resulted in considerable dehydration of the goods, and would not meet the current requirements of today's markets.
Rainey, in U.S. Pat. No. 3,940,062, attempted to improve the situation by packaging moisture pods with the perishable goods in a stagnant environment.
Rhoad, in U.S. Pat. No. 3,961,925, devised a very elaborate means for spraying a recycled liquid coolant, such as chilled brine, directly onto the perishable goods during transportation and storage, to address the needs of cooling and humidification without success.
Rath, in U.S. Pat. No. 4,003,728, specifically targeted product spoilage through dehydration caused by refrigeration systems recycling dried air around the perishable goods. Rath provided an opportunity for condensate from the refrigeration system to be absorbed by the stream of circulated air. In this regard, Rath provided a humidity sensor in the ducted stream of air coming into the cargo container and passing through a duct along the bottom of the container and up through vents. This duct also contained condensate, and excess was disposed of through floor drains. The air moved upward around the goods and was collected by a return duct and passed into the front equipment section and downward through the refrigeration (or heating) unit. One problem with Rath's approach is that if the relative humidity sensor reading dropped below the stated value (preferably 80% relative humidity), only an alarm would be lighted. Such an alarm was not likely to be seen deep in a cargo hold of a ship, or by a driver of a truck, or by a railroad engineer, and, if not seen, no positive action could be taken. A second problem was that the position of Rath's moisture sensor was located only a few inches above the surface of water from condensation collected in the duct and quite likely never dropped below a reading of 80% relative humidity, regardless of a much lower humidity level around goods at the top or middle of the cargo. A third problem is that Rath notes excess water that collected in the duct was drained from the cargo container through a floor vent. Since this water came from the perishable goods, Rath's process was also dehydrating the goods to a considerable extent. It is further noted that Rath's system has poor humidity pick up from the surface of the water (i.e., negligible quantities of moisture would be reabsorbed by the circulating air stream) at the low temperatures the refrigerated perishable goods containers will operate, due to the low water vapor pressure and the relatively low surface area of the water-atmosphere interface.
Burg, in U.S. Pat. No. 4,655,048, describes a hypobaric preservation of non-respiring animal matter by contacting the storage atmosphere with a body of heated water and very carefully controlled pressures slightly less than the vapor pressure of water at the storage temperature in sealed containers. Such an approach simply is not practical for bulk transport and holding of perishable goods.
Edwards, in U.S. Pat. No. 4,808,303, describes a produce hydration system for use in display racks in which water is carefully filtered, pressurized and efficiently sprayed or misted over the surface of exposed produce in display racks. While providing interesting technology related to spraying, Edwards fails to teach how to maintain proper humidification during transportation and holding of perishable goods.
Wallace, in U.S. Pat. No. 4,884,411, describes a high humidity refrigeration apparatus that is fitted into one end of a shipping container. At the top of a vertical casing or duct is a water spray assembly. Below the casing or duct is a cooling section, below which is mounted a heating section, below which is a water reservoir. Water is pumped from the reservoir to the spray assembly from which it falls on the cooling section and then on to the heated section. Air enters this unit just above the water level in the reservoir, and passes upward over the heating section where it is warmed and can pick up humidity. The air is then passed up over the cooled section where it is cooled and excess water is condensed from the air and falls back to the reservoir. The air then continues upward past the spray assembly and on to the produce section in a horizontal direction and is brought off the top and is cycled back to repeat the process. Those familiar with thermodynamics will recognize the process could achieve saturated, cooled air if the flow rate of the air were slow enough relative to the size of the heating and cooling sections; however, the energy efficiency in doing so would be very poor and the capacity of the system would be limited to low demands for cooling and humidification. Transportation costs of perishable goods would be high because of the required large size and weight of the unit relative to the mass of cargo it can service.
Spruill, in U.S. Pat. No. 5,037,459, teaches the use of a quantity of a salt solution in communication with the atmosphere in a substantially closed container to maintain a desired level of humidity. The required bulk and weight of such a solution would be prohibitive for portable perishable goods containers in regards to both cost and space.
Coffield, in U.S. Pat. No. 5,127,233, teaches moisture recovery from compressed air by means of a filter. Such moisture is then supplied to the atmosphere around the foodstuffs. This method is energy inefficient, and is not the subject of the instant invention.
Podd et al., in U.S. Pat. No. 5,529,177, teaches the use of saturated desiccant panels for gradually releasing humidity in containers. This method is a very weight intensive approach to transportation containers, and lacks the immediate control for supplying humidity on demand.
Kleinberger et al., in U.S. Pat. No. 5,762,661, describes a way to refine a mist in a humidification system. Such refinements are not a part of the instant invention.
Fractal, Inc., according to their product specification sheet, offers a state-of-the-art humidificati
Baker, Jr. Russell
Briscoe, Jr. Charles Eugene
Herlihy Peter
Benesch Friedlander Coplan & Aronoff LLP
CA Global Express, LLC
Wayner William
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