Air Curtain

Air curtain for open-fronted refrigerated showcase

Air Curtain Abstract
A refrigerated showcase has a front opening through which a consumer can view and access foodstuffs on display. The foodstuffs are cooled by coolant air introduced through a slanted, perforated, interior panel located near a rear wall of the showcase. An air curtain directed downwardly at the front opening minimizes coolant air loss through the opening. Lips are applied and extended from the edges of vertical sides of the access opening to reduce the loss of coolant air through the air curtain. Thus, relative flows of coolant air and the air curtain are maintained inside the showcase.

Air Curtain Claims
I claim:

1. An auxiliary air handling mechanism comprising:

(a) refrigerated display case housing having a substantially vertical air curtain, a refrigerated product display compartment and a product storage area disposed below said refrigerated product display compartment;

(b) a perforated panel spanning the length of said refrigerated product display compartment and said product storage area;

(c) a first plenum disposed in said display case housing adjacent to the perforated panel and opposite said refrigerated product display compartment;

(d) means for dividing air from said first plenum into a first portion to flow substantially horizontally through said perforated panel into said refrigerated product display compartment and a second portion to flow substantially horizontally through said perforated panel into said product storage area and into said substantially vertical air curtain; and

(e) a second plenum attached to the perforated panel and arranged adjacent to the air dividing means, said second plenum receiving the first portion of air from the air dividing means.

2. The mechanism of claim 1 wherein the air dividing means is also attached to the perforated panel.

3. The mechanism of claim 2 wherein the air dividing means has an open bottom means for receiving the first portion of air from an air source.

4. The mechanism of claim 1 wherein said first plenum has an open top means for receiving the first portion of air from the air dividing means.

5. The mechanism of claim 2 wherein the air dividing means extends farther from the perforated panel than the second plenum.

6. The mechanism of claim 1 wherein the second plenum is also attached to the air source housing.

7. The mechanism of claim 1 wherein the air dividing means extends over part of said air source housing so as to receive the first portion of air from the air source.

8. The mechanism of claim 7 wherein the air dividing means has an open bottom means for receiving the first portion of air from the air source.

9. The mechanism of claim 7 wherein said second plenum has an open top means for receiving the first portion of air from the air dividing means.

10. The mechanism of claim 1 wherein said perforated panel is inclined away from said refrigerated product display compartment to form a tapered first plenum.

11. A refrigeration device comprising:

(a) a refrigerated showcase having a top, a bottom, a front, a rear wall, a refrigerated product display compartment and a product storage area disposed below said refrigerated product display compartment;

(b) a perforated panel disposed inside the showcase between the front and rear wall said perforated panel extending the length of said product display compartment and said product storage area;

(c) an air source arranged in a housing adjacent to the perforated panel;

(d) means for dividing air from the air source into a first portion to flow through said perforated panel to cool said product storage area and a second portion to flow through said perforated panel to cool said refrigerated product display compartment;

(e) a first plenum attached to the perforated panel and arranged adjacent to the air dividing means and said product storage area, said first plenum receiving the first portion of air; and

(f) a second plenum disposed between the rear wall of the showcase and the perforated panel and adjacent said refrigerated product display compartment, said second plenum receiving the second portion of air.

12. The device of claim 11 wherein an air curtain is disposed in the front of the showcase.

13. The device of claim 12 wherein the air curtain is directed downwardly so as to prevent escape of cooled air inside the showcase.

14. The device of claim 11 wherein the air dividing means is also attached to the perforated panel.

15. The device of claim 11 wherein the first plenum has an open top means for receiving the first portion of air from the air dividing means.

16. The device of claim 15 wherein the open top means of the first plenum is also attached to the housing for the air source.

17. The device of claim 11 wherein the air dividing means has an open bottom means for receiving the first portion of air from the air source.

18. The device of claim 17 wherein the air dividing means extends over part of the housing for the air source.

19. The device of claim 18 wherein the first plenum is also attached to the housing for the air source.

20. The device of claim 11 wherein the air source directs cooled air upwardly through the second plenum, across the top of the showcase, and then downwardly in the front thereof to form an air curtain.

21. In a cooling machine having a display showcase, a top, a bottom, a front, a rear wall, a perforated panel disposed between the front and rear wall, a vertical plenum behind the perforated panel, and means for circulating cooled air in the vertical plenum from the bottom and through the perforated panel, wherein the improvement comprises:

(a) an air divider arranged in an inwardly tapering vertical plenum to separate the cooled air into a first portion to flow through said perforated panel into a refrigerated product storage compartment and a second portion to flow through said perforated panel into a refrigerated product display showcase; and

(b) an auxiliary plenum attached to the perforated panel adjacent to the air divider so that the first portion of the cooled air may be directed into a refrigerated storage compartment in said refrigerated product display showcase.

22. The machine of claim 21 wherein the air divider is also attached to the perforated panel.

23. The machine of claim 21 wherein the auxiliary plenum is secured to the circulating means.

24. The machine of claim 21 wherein the auxiliary plenum has the open top means for receiving the first portion of the cooled air from the air divider.

25. The machine of claim 24 wherein the open top means of the auxiliary plenum is secured to the circulating means.

26. A refrigeration device comprising:

(a) a refrigerated display case housing having a top, a bottom, a front, a rear wall and a refrigerated product display and a refrigerated product storage area disposed below said refrigerated product display;

(b) a perforated panel extending the length of said refrigerated product display and said refrigerated product storage area;

(c) a tapered plenum tapering upwardly and inwardly from said bottom of said refrigerated display case to the top of said refrigerated display case;

(d) an auxiliary tapered plenum disposed below said tapered plenum; and

(e) a diverter disposed in said tapered plenum intermediate said refrigerated product storage area and said refrigerated product display to divert one portion of cooled air to said refrigerated product storage area and another portion of said cooled air to said auxiliary tapered plenum and said product storage area.

27. The refrigeration device of claim 26 further comprising an evaporator device disposed at the bottom of said refrigerated display case housing.

28. The refrigeration device of claim 27 further comprising an evaporation tray disposed below said evaporation device.

29. The refrigeration device of claim 28 further comprising a condenser disposed at the top of said refrigerated display case.

30. The refrigeration device of claim 29 wherein water collected in said evaporation tray is pumped to said condenser to cool said condenser.

Air Curtain Description
BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates broadly to refrigerated showcases, particularly open-fronted display and storage cases with air curtains. More specifically, the present invention relates to a refrigerated showcase having an opening through which a consumer can view and access stored items on display and to such a showcase wherein cooling air is introduced through a perforated interior panel with the coolant air maintained within the refrigerated compartment by an air curtain passed downwardly within the showcase opening.

2. Description of the Related Art

An example of this type of showcase is described in U.S. Pat. No. 3,696,630 granted on Oct. 10, 1972, to Bressickello who discloses various self-service showcases constructed with front access openings for the purpose of displaying comestibles such as meat, eggs and vegetables. In such showcases, the cooling system includes a refrigerant coil, also known as an evaporator coil, which is located in such position so as to cool air circulating through the showcase.

The refrigerant coil is sometimes oriented above a relatively small drip pan, also referred to as a dissipater pan situated in a location so as to collect condensation from the coil. When the water level rises to a predetermined level, this condition is sensed and a pump is activated to lift the water to an overhead dissipater pan arranged on top of the showcase. The dissipater pan may include a heating coil to dissipate any accumulated water. Other showcases eliminate condensation from the refrigerant coils by a drainage system that communicates with a floor sink.

An example of a showcase of the type where condensation from the evaporator coil is pumped to a dissipater pan arranged on top of a cabinet of the refrigerated showcase is illustrated in U.S. Pat. No. 4,766,737 granted on August, 1988, to Baxter, II. In this prior art device, a high temperature coil of the condenser assembly is associated with the lowermost of an array of dissipater pans in order to effect the transfer of heat to the condensate which has been pumped up to the dissipater array atop the cabinet of the refrigerated showcase.

The open-fronted, refrigerated showcases with air curtains in the prior art have reached a level of efficiency such that additional improvements are not readily achieved.

It is well known in the prior art to use perforated wall dividers and/or rear panels which are angled to form an air plenum in association with the back of the showcase. These air plenums are shaped to have a decreasing volume through which cooled air is passed upwardly with the flow also passing through perforations in the wall dividers into the refrigerated showcase. This feature is illustrated in U.S. Pat. No. 3,696,630 previously mentioned and in U.S. Pat. No. 5,345,778 issued on Sep. 13, 1994, to Roberts.

It is also known to route cooled air to a bottom portion of cooling compartments where foodstuffs are stored. Bottom storage bins, where foodstuffs are placed to replenish the display shelves located above the storage area, are commonplace. However, cooling the storage area is difficult to do. Prior art devices have cooled the storage are by diverting a portion of the cooled air which is flowing upwardly from housings in which evaporator coils and air-moving fans are arranged. An example of such an arrangement is found in U.S. Pat. No. 5,345,778 just mentioned.

SUMMARY OF THE INVENTION

In accordance with the present invention, three methods of improving air curtains in open-fronted refrigerated showcases have been incorporated in the refrigerated compartment, in the refrigerant system atop the cabinet, and in the air circulation system.

As shall be fully explained below, one purpose of the present invention is to achieve optimal heat exchange by continuously trapping particles suspended in the air that flows into the components of the refrigerant system which over time becomes fouled and impedes air flow and/or the efficiency of the heat exchange. In particular, an air filter is used atop the showcase. This air filter and precondenser coils, situated beneath the air filter, are both exposed and susceptible to fouling. Advantageously, these elements of the present refrigeration system are cleaned by condensate originating at the evaporator coils. This condensate is pumped from a lower drip pan up to the top of the showcase, then expelled over the air filter. The condensate then travels from the air filter over the precondenser coil into the dissipater pan. The precondenser coil, preferably made of copper tubing, is inserted between the compressor and the condenser coil. As the refrigeration gas is sucked from the evaporator coil, the compressor places the gas under a higher pressure, thus raising the gas temperature. The hot gas is then pushed into the precondenser coil which has a sufficient length to evaporate the water that lands in the dissipater pan. The lengthy copper tubing coil between the compressor and the condenser coil functions to evaporate the water which has collected during the operation of the refrigerated showcase. The precondenser coil is situated in the dissipater pan, suitably resting on the bottom of the pan, with at least a portion of the coil exposed to the atmosphere in the open section of the top of the showcase. The precondenser coil also sits forward of the face of the air filter. Preferably, a major portion of the precondenser coil is exposed to the atmosphere. The precondenser coil also assists the condenser coil by precondensing the refrigerant. The air is pulled through the space where the filter, precondenser and dissipater pan is located. The air then circulates outside the precondenser coil and acts as a heat exchange medium. Precondensing refrigerant gas into liquid, moreover, makes the condensing system more efficient.

Another aspect of the present invention, as shall also be further explained below, is to minimize coolant air loss through the showcase opening. This advantage is achieved by a method of identifying, measuring, and ameliorating coolant air loss by providing a lip along vertical sides of the opening in the refrigerated compartment. The lips extend vertically along at least a portion of each of the two vertical sides of the opening where, as it has been discovered, the loss of cooled air from the refrigerated compartment is greatest.

The present invention also provides an apparatus for assuring proper cooling at the bottom of the refrigerated compartment of the showcase.

A further aspect of the present invention relates to the use of an air divider and plenum arrangement which directs the coolant air through perforations in the back of the refrigerated compartment so that the coolant air flows over foodstuffs which are stored at the bottom of the refrigerated compartment in an area beneath the lowermost display shelf. In other words, a diverter and plenum arrangement is utilized to achieve routing of the coolant air to the bottom of the refrigerated compartment below the lowermost display shelf in a facile manner.

It has also been found that, in refrigerated showcases wherein there is an opening in the front thereof through which a consumer can view and access foodstuffs on display, these foodstuffs in the showcase are cooled by cold air introduced from a perforated panel. Such refrigerated showcases include an air curtain generated within and directed downwardly from the top of the opening. After a determination of the flow rate, the loss of coolant air through the air curtain can be either reduced or prevented altogether by using lips that extend from the vertical edges partially into the opening.

The following method can be used to determine the dimensions of the lips that limit coolant air loss through the air curtain. In open-fronted, refrigerated showcases, a 4" lip on each side has been found suitable to minimize the coolant air loss along the vertical edges of any refrigerated compartment which has an opening of about 56" in height. The method of determining the size of the lips needed for the vertical edges involves several steps.

First, load the refrigerator shelves with the product to be refrigerated and displayed, preferably at a desirable product temperature sufficient to avoid the possibility of spoilage. Actually, this step can be omitted, but it is preferred to use a stocked compartment.

Second, adjust the rate of flow of the coolant air to obtain a stable air curtain. This step is achieved by producing a nominal air flow of 500 cubic feet per minute by four pans which are each rated at 125 cubic feet per minute so that an actual air flow rate of about 330 cubic feet per minute is obtained.

Third, introduce a visible additive, such as artificial smoke to the circulating air in order to enable observation and identification of any air escaping at the periphery of the front opening.

Fourth, apply a first lip extending from one vertical side edge into the opening and a second lip extending from another opposite vertical side edge into the same opening.

Fifth, observe, by increasing and/or decreasing, the extension of the lips into both side edges of the opening. When the escape of air through the air curtain is minimized at the vertical periphery of the opening in the refrigerated showcase, the optimal lip size has been empirically determined.

The lips are then affixed to the vertical side edges which extend into the opening in the showcase a distance based on the observations made in order to limit the loss of coolant air through the air curtain.

Thus, in accordance with the present invention, the loss of coolant air through the air which is passed over the displayed products is minimized. The coolant air then emerges from the refrigerated compartment for recycling with the circulating air forming the air curtain at the opening in the showcase. As heretofore noted, the optimum conditions for operation and determination of lip size are identified empirically by observing and adjusting the size of the lips which minimize the loss of coolant air at the vertical peripheries of the opening in the refrigerated compartment.

Furthermore, the controlled flow of coolant air through perforated openings in the panel is facilitated by an air divider and plenum arrangement that provides for adequate contribution of the coolant air the food storage area which is located at the bottom of the refrigerated compartment, typically beneath the first storage shelf. As air is ejected upwardly by the four fans in the fan housing, the air is pushed between the back wall which is plumbed straight and the perforated panel which is inclined slightly backwards by approximately six degrees from its vertical axis. The perforated panel has at its lower end the air divider and plenum arrangement situated beneath the first display shelf. The air divider and the plenum arrangement are installed to force air flow through the perforated panel into the bottom storage section of the refrigerated compartment. Thus, air flow equilibrium throughout the perforated panel, including the bottom storage section of the refrigerated compartment, is accomplished. This equilibrium is achieved by forcing air to be approximately the same amount in all spaces where the products are placed. The reason for this result is believed to be that the air travels fastest when it is nearest to the fans, so that the air travels to the upper part of the panel and crosses through the perforations with great ease.

The multiple fans, which move cooled air over the evaporator coils situated in the bottom of the refrigerated compartment, reduce condensation on the evaporator coils that are used to cool the air circulating in the showcase so that icing is reduced on the evaporator coils.

Water collecting on the evaporator coils is captured in an evaporation tray situated below the evaporator coils and is pumped to the top of the showcase where the condenser is located. At the top, the water sequentially is passed over a filter which functions as a water evaporator and also functions to remove particulate matter and other foulants, whereby the water from the evaporator coils functions both to clean the filter and to cool the air passing through the filter before the air contacts the condenser coils of the refrigeration system. The water runs from the filter to the dissipater pan and then to the precondenser coils carrying refrigerant from the compressor. These precondenser coils are thus cooled by cold water originating at the evaporator coils. The filtered air passing over the condenser coils, which air is further cooled before contact by the water, passes over and/or through the filter before absorbing heat produced during refrigerant condensation. At the same time, the rate of evaporation from the dissipater pan lying under the precondenser coils is substantially increased and the risk of water overflow is minimized. The heat generated during compression is exchanged through both the condenser coils and the precondenser coils which comprise another set of coils located downstream of the condenser coils. The precondenser coils in essence function as heating coils to assist in the evaporation of water from the dissipater pan using the heat of condensation, thereby providing two desirable fictions using energy available within the refrigeration system itself, namely removing heat from the compressed refrigerant and adding heat to the condensate which accumulates in the dissipater pan.

Furthermore, the present invention relates to a self-service refrigerated showcase having therein an enclosure for the display of cooled foodstuffs. The enclosure has a front access opening defined by top, side, and bottom housing panels. At its sides, the enclosure is defined by vertically elongated strips corresponding to the side housing panels. This enclosure provides access to the foodstuffs on display.

Also, the enclosure has other advantageous features. For example, there is a perforated panel through which coolant air is introduced and passed over the foodstuffs. Also, there is a top panel having near to the forward part thereof a structure for forming an air curtain which moves coolant air downwardly within the front access opening after diverting the coolant air from the perforated panel. This coolant air originated from a space behind the perforated panel before reaching the access opening.

In accordance with the present invention, a structure is provided for minimizing air loss through the front access opening. This structure is a lip extending from each of the housing side walls along at least a portion of the length of the opening. In this way, coolant air loss which has been observed to occur predominately at the vertical periphery of the opening is substantially prevented.