Refrigeration – Means producing shaped or modified congealed product – With raw material projector – e.g. – spray
Reexamination Certificate
1999-10-20
2001-03-27
McDermott, Corrine (Department: 3744)
Refrigeration
Means producing shaped or modified congealed product
With raw material projector, e.g., spray
C062S352000
Reexamination Certificate
active
06205807
ABSTRACT:
TECHNICAL FIELD
This invention pertains to the field of ice cube making machines, and in particular to a low cost, high-performance ice making evaporator design.
BACKGROUND OF THE INVENTION AND PRIOR ART
Ice machines are widely used in restaurants and the like for producing ice, in the form of flakes, chips, cubes, etc. for use in beverages and for other uses relating to food and drink services. Generally, these ice machines include a refrigeration apparatus for freezing water supplied to the machine, a means for periodically removing, or “harvesting” ice from the freezing surface, and a cabinet or bin for storing the ice until it is needed.
In a typical ice making apparatus, water is brought in contact with a refrigerated surface, usually referred to as the evaporator, to be frozen. Freezing takes place for an interval of time, typically fifteen to twenty minutes, until the size of the ice cube is adequate. At this point, the harvesting operation takes place to remove the cubes from the evaporator. When harvested, the ice cubes typically fall off of the evaporator and are directed into an ice holding bin.
Ice making evaporators are typically constructed using stainless steel or nickel-plated copper. These materials are used because of their suitability for use with potable water and their heat transfer characteristics. Copper for example, is an excellent conductor of heat and therefore is well suited for use in ice machines. Stainless steel is also used extensively in ice making evaporators because of its non-corroding properties and suitability for contact with potable water. While these materials are well suited for use in ice machine evaporators, they can be expensive to use and fabricate.
An example of an ice making evaporator that is commercially available is provided in U.S. Pat. No. 4,458,503 to Kenneth L. Nelson. This patent describes an ice making evaporator consisting of a serpentine copper tube to which a series of formed, nickel-plated copper strips are attached. The entire assembly is placed into an injection mold and molded over with a plastic material. All of the copper tubing and portions of the copper strips are molded over with plastic. Other portions of the copper strips are left bare (free of plastic) to provide a good heat transfer path from the water and ice to the refrigerant. These bare portions of the evaporator plate provide the locations where the ice cubes form.
Another example of a commercially available ice making evaporator is provided in U.S. Pat. No. 5,479,707 to Alvarez, et al. This patent describes an evaporator constructed from sheets of stainless steel which are stamped, punched and then welded together to create a flat-walled serpentine refrigerant passage. This stainless steel serpentine is placed into an injection mold and molded over with a plastic material to create ice cube formation sites of the desired shape. The stainless steel is left exposed in the locations where ice is to form so as to improve heat transfer. In this design the ice cubes form on these exposed areas, which are also the stainless steel walls of the refrigerant passage.
Both of the evaporator designs referenced above utilize relatively expensive tooling, processes and materials to create the evaporator assemblies.
A primary objective of this invention is to utilize materials and manufacturing processes that are inherently low in cost in order to reduce substantially the cost of an ice making evaporator.
Another primary objective of this invention is to optimize the heat transfer performance of the evaporator assembly through its ice forming geometry and refrigerant circuiting.
Another primary objective of this invention is to minimize the thermal mass of the evaporator assembly. Since an ice machine evaporator is constantly cycled between hot and cold temperatures, lowering the thermal mass of the assembly will result in less energy being needed to heat and cool the assembly between those temperatures.
Another primary objective of this invention is to provide a freezing surface that meets the ice machine sanitation requirements of the National Sanitation Foundation (NSF).
The present invention achieves these objectives utilizing a uniquely formed aluminum roll-bond type evaporator plate to which is attached a grid of plastic ridges which form an array of ice cube forming sites on both sides of the plate. This plastic grid is comprised of thin vertical ridges and wider horizontal ridges. The vertical ridges act to separate horizontally-adjacent cube forming locations. The horizontal ridges act to separate vertically-adjacent cube forming locations and to cover the refrigerant passages of the roll-bond evaporator plate. Additional features not previously used in ice making evaporators are also incorporated into the present invention to improve ice-making performance and allow this configuration to be easily manufactured.
The low cost of the aluminum evaporator plate, the low thermal mass of the assembly, the geometry of the ice cube forming locations and the additional ice making improvements incorporated in this design provide superior heat transfer performance and significantly lower cost than existing ice making evaporator designs.
SUMMARY OF THE INVENTION
The invention herein comprises an ice making evaporator which can be inexpensively assembled with a novel combination of components manufactured with mature and relatively inexpensive manufacturing technologies. Harvesting ice from this evaporator is done using the traditional hot gas method, and requires no additional valves, piping, controls or moving parts.
As used herein, the term “cube” shall not be limited to describing a regular solid piece of ice with six sides, but includes solid pieces of ice of any suitable shape.
In the preferred embodiment, an aluminum roll-bond type evaporator plate serves as the core of the evaporator assembly. This type of evaporator is lightweight, low cost and has a low thermal mass (thermal mass being equal to the weight of the materials used multiplied by their specific heat). It is of a type commonly found in domestic household refrigerators. This type of evaporator is basically a flat sheet of aluminum having an integrally formed serpentine refrigerant passage running through it.
To complete the evaporator assembly, a plastic gridwork is attached to either side of the aluminum evaporator plate. This plastic grid forms an array of exposed aluminum areas each separated from the next by ridges of plastic. In operation, ice will form on the exposed aluminum areas (freezing sites), and will tend not to form on the significantly less conductive plastic ridges.
In addition to the novel configuration of the refrigerant passages and the plastic grid, there is another feature that further improves the reliability of the evaporator. A water distribution tube mounted on the top of the evaporator is uniquely configured to direct water through small upward-facing distribution holes in order to supply a stream of water to the surface of the evaporator. Since the water distribution holes are the smallest orifices though which the ice making water circulates, these holes tend to act as a filter, catching whatever debris is floating or suspended in the water. Making these holes upward facing allows them to be effectively flushed-out each time the water flow through the water tube is stopped.
Since the water flow is typically stopped during each ice making cycle, the water in these upward facing holes will reverse (flowing backwards) each ice making cycle. This back-flow of water will tend to flush out any debris caught in the holes. Also, as the flow of water may have been the only thing holding the debris in the hole in the first place, stopping the water flow will allow gravity to help clear debris from the holes. Thus by utilizing upward facing holes, the water distribution tube has been effectively transformed into a “self-cleaning” water tube.
REFERENCES:
patent: 2677249 (1954-05-01), Mason
patent: 4649718 (1987-03-01), Linstromberg et al.
patent: 4986088 (1991-01-01), Nelson
patent
Ali Mohammad M
Gibson Dunn & Crutcher, LLP
McDermott Corrine
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