Refrigeration – Using electrical or magnetic effect – Thermoelectric; e.g. – peltier effect
Reexamination Certificate
2000-03-14
2001-10-02
Bennett, Henry (Department: 3744)
Refrigeration
Using electrical or magnetic effect
Thermoelectric; e.g., peltier effect
C062S457900
Reexamination Certificate
active
06295820
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a device for chilling fresh fruit and other fresh food products and, more particularly, to an improved countertop fruit chiller utilizing a Peltier effect thermoelectric device.
Thermoelectric devices operating in accordance with the well known Peltier effect have been used as cooling/heating devices for many years. Such a thermoelectric device comprises an array of semiconductor couples connected electrically in series and thermally in parallel. The semiconductor couples are sandwiched between metalized ceramic substrates. When DC electric current is applied in series to the thermoelectric device, it acts as a heat pump with heat being absorbed on the cold side, thereby cooling it, while heat is dissipated at the other side, where the temperature rises. Reversing the current causes the direction of heat flow to be reversed. The efficiency of the thermoelectric device may be enhanced by attaching a heat sink and a cold sink to the respective hot and cold sides.
Peltier effect devices have long been used to provide coolers and/or heaters for keeping foods fresh or for warming foods for serving. It has also been found and is well known to use forced air convection to aid in heat transfer. A small electric fan is typically used to circulate air past the cold sink and into and through a container for the food, while another fan moves ambient outside air across the heat sink to dissipate heat from it.
Although chillers for fresh fruit and other perishable food products are well known in the art, the market success of such devices has been limited. There appear to be a number of reasons for this lack of market success. One is the cost and heat transfer efficiency of the solid state thermoelectric modules. In addition, such prior art modules have typically been quite fragile, exhibiting low mechanical strength. In addition, the need to provide circulation of cool air to attain the greatest cooling efficiency, has led to complex duct systems which add substantially to the cost of the containers, typically made of molded plastic materials. Long air circulation flow paths also result in heat loss and pressure drop, both of which decrease the efficiency or add to the cost by requiring larger thermoelectric modules.
SUMMARY OF THE INVENTION
In accordance with the present invention, a chiller for fresh fruit or other perishable food products utilizes a construction which optimizes a cooling air flow and thus heat transfer efficiency with a container construction that is less expensive to manufacture and permitting the use of a relatively smaller thermoelectric module. Thermoelectric modules of increased efficiency and improved mechanical strength, such as disclosed in U.S. Pat. No. 5,448,109, are particularly suitable for use in the fruit chiller of the subject invention.
In its broadest aspect, the food chiller of the present invention comprises a supporting base that includes a housing for mounting a Peltier effect thermoelectric module sandwiched between a cold sink and an opposite heat sink. The housing also defines an upwardly opening cooling duct system that includes a cool air supply duct in heat transfer communication with the cold sink, a return air duct, and a cool air circulation fan in the cooling duct system to circulate air therethrough. A food container is supported on an upper peripheral edge of the housing, the container having an upper enclosing side wall above the peripheral edge of the housing and a lower bottom wall within said peripheral edge, the bottom wall forming an enclosing top wall for the duct system. The bottom wall has formed therein a plurality of inlet holes that communicate with the cool air supply duct and a plurality of outlet holes that communicate with the return air duct.
In one embodiment of the invention, one of the cooling system ducts is positioned to extend along an outer peripheral wall of the housing that includes the housing peripheral edge. The other of the ducts is centrally disposed within the first duct and separated from it by a generally vertically extending common dividing wall. The duct system also includes a cool air duct inlet, a return air duct outlet, and a recirculation passage that includes a circulation fan and the cold sink. The recirculation passage interconnects the cool air duct inlet and return air duct outlet. Preferably, the first outer duct comprises the cool air supply duct and has a generally horizontal lower enclosing wall that forms a common separating wall with the recirculation passage which is disposed below the separating wall. The cool air duct inlet is formed in the common separating wall adjacent the outer peripheral wall of the housing. The return air duct outlet is preferably also formed in the common separating wall. In a preferred embodiment, the common separating wall is generally horizontally disposed and generally parallel to the lower bottom wall of the container (also forming the top wall of the duct system and spaced vertically above the common separating wall).
In one alternate embodiment of the invention, the food container bottom wall includes a hollow central tower that extends vertically upwardly within the interior of the container. The central tower is provided with a plurality of holes which may comprise either the inlet holes for the cool air supply duct or the outlet holes for the return air duct. In this embodiment, the holes preferably comprise a hole pattern of increasing hole size in an upward direction along the tower.
In a presently preferred embodiment, the cooling duct system has a lower enclosing wall that forms a common separating wall with the recirculation passage disposed below the separating wall. Either of the cool air duct inlet or the return air duct outlet may be formed in the common separating wall immediately adjacent the outer peripheral wall of the housing. The plurality of inlet holes or outlet holes formed in the enclosing top wall of the duct that extends along the outer peripheral wall of the housing comprises a hole pattern of increasing hole size with increasing distance from the respective duct inlet or duct outlet. Preferably, the cool air supply duct is positioned along the outer peripheral wall of the housing.
The food container is removable from the housing and is provided with an annular outer edge seal between the upper peripheral edge of the housing and the lower edge of the enclosing side wall of the container. An annular inner seal is disposed between the upper edge of the common dividing wall and the underside of the container bottom wall. The outer seal may be attached to the upper peripheral edge of the housing and the inner seal to the underside of the bottom wall. Alternately, both outer and inner seals may be secured to the container bottom wall.
In the embodiment in which either the cold air duct inlet or the return air duct outlet is formed in the common horizontal separating wall adjacent the outer peripheral wall of the housing, the other outlet or inlet is also formed in the common separating wall in approximately the center thereof. The respective pluralities of inlet holes and outlet holes, in another embodiment, are interrupted to define solid wall portions that overlie the cool air duct inlet and the return air duct outlet to cover and protect the same from the ingress of debris.
The container is normally closed with a removable cover such that cooling air is continuously recirculated. In one embodiment, however, an outside ambient air supply conduit communicates with the recirculation passage and includes a metering device to admit a controlled flow of outside air to assist in purging the cooling duct system of ethylene gas and other ripening by-products of fruit. The metering device may comprise a small diameter tube connected to the recirculation passage upstream of the fan.
In the embodiment of the invention in which the food container includes a central tower, an auxiliary food tray may be demountably supported on the tower above the container bottom wall. The central tow
Bruner Dan M.
Cauchy Charles J.
Clark George A.
Gundlach Douglas P.
Thompson Mark S.
Andrus Sceales, Starke & Sawall
Bennett Henry
Delta T, LLC
Jiang Chen-Wen
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