GB2126697A - Refrigerated display cabinets - Google Patents

Abstract

In an open-front refrigerated display cabinet, a cooled air circulation system provides an air curtain across the open front and includes a perforate rear wall 42 to direct an air flow 44 into the cabinet storage space, baffles 46, 48, 50 being provided to deflect the air flow 44 upwards and then outwards towards the air curtain. <IMAGE>

Description

SPECIFICATION Improvements relating to refrigerated display cabinets This invention relates to refrigerated display (and dispensing) cabinets, and in particular concerns a method of maintaining such display cabinets in cool or refrigerated condition.

Refrigerated display cabinets for food products and produce are well known and are in extensive use in supermarkets and shops. These cabinets comprise essentially a base, a rear wall, a top wall and shelving, the front being open to permit access by customers or shop assistants for the extraction of the products and produce.

The cabinet also includes a refrigeration system in order to keep the products cool, to maintain their freshness, and the required temperature of the cabinet interior is dictated by the products or produce to be held there. For example for fresh meat, the temperature should ideally be of the order of OOC for dairy products +4 C, for fruit and vegetables 60C, for ice cream -230C, and for frozen meat -1 00C and soon. A tolerance limit plus or minus 20C is usually allowed.

In order to keep the interior of the cabinet cool, it is usual to provide a cold air circulation, of which the circulating air is passed over an evaporator of a refrigeration system housed in the cabinet so that the cold air is passed into the interior of the cabinet. In order to isolate the interior of the cabinet from the ambient air, it is usual to provide that a portion of the circulating air is passed as a curtain from the front edge of the top of the cabinet, across the open front and to an inlet duct at the bottom front edge; the curtain of air is collected and recirculated. In one type of cabinet arrangement, a second portion of the circulating air is simply led through a perforated rear screen so as to flood into the interior of the cabinet whilst another portion is used to form the said curtain.The air which floods into the interior of the cabinet through the perforated screen is collected at the bottom of the cabinet and recirculated.

Another type of arrangement involves the provision of two or three curtains of air of differing temperature in order to form an effective insulator to the ambient air, and also to keep the air inside the cabinet at a low temperature.

The first form of cabinet works satisfactorily in a range down to about OOC, but below this temperature the formation of frost takes place to an accelerated extent by the extraction of the moisture from the air and by the contact of same with the cold surfaces. Additionally, frost deposits on the evaporator to such an extent as to limit the air circulation and the equipment simply becomes unacceptably inefficient.

The second form of equipment having multiple air curtains across the front does not suffer from this disadvantage, because the air curtains effectively form an insulator between the interior of the cabinet and the ambient air, but the disadvantage of the multi-air curtain equipment is that it is extremely expensive, and is liable to frequent breakdowns, making maintenance expensive and troublesome.

The present invention seeks to provide a refrigerated cabinet needing no more than a single insulated air curtain across the open front but which is more effective than the first known type in maintaining a lower temperature inside the cabinet and yet does not suffer from the disadvantages of the multi-air curtain type of cabinet.

The present invention provides a refrigerated display cabinet of the type to which access is gained through an open front, and in which there is an air circulation cooling system to keep the contents cool, such air circulation cooling system providing an air curtain across said open front to insulate the cabinet interior from the atmosphere, and also including means to cause issuance of air from a perforated rear wall of the cabinet into the cabinet interior space over a support surface for goods to be contained in the cabinet, said cabinet including deflection means to deflect the air issuing from said rear wall upwardly then outwardly over the said space to meet the said air curtain and cause the creation of eddy currents in the said space.

Trials with this modified construction have been extremely encouraging and in trial cabinets sustained temperatures of --1 0 C without excessive frosting of the evaporator and the plates forming the storage space have been achieved.

In a preferred arrangement, the unit will be a multi shelf unit, and there will be a deflector above each shelf and also from the base of the storage space to under the lowermost shelf. The cabinet back may be perforated as in a conventional arrangement with the deflectors fitted in relation thereto so that the deflectors in effect redirect the air coming through the perforated back panel.

The deflector means may be an angled sheet of metal having on one side thereof insulating material, the insluating material being arranged to face the cold air as it emerges from the perforated back panel so as to prevent the metal sheet from being cooled to dew point.

The provision of outlets defined by the deflection means above the respective shelves and the base panel results in that a plurality of individual eddies of air flow exist in the cabinet space above the base panel and the respective shelves.

The air curtain across the front of the cabinet assists in maintaining the eddy flows as these will be travelling in the same direction as the air curtain where they are adjacent the air curtain.

An embodiment of the invention will now be described with reference to the accompanying diagrammatic drawing of which the single figure is a sectional elevation through a refrigerated cabinet of the type which the invention relates.

Referring to the drawings, it is to be mentioned that the structural layout of the cabinet may change without departing from the scope of the invention and the form illustrated is only one example. Additionally, the figure does not show the various other components of the cabinet, such as the insulation as may be provided in the base, rear and top of the cabinet, or the other control components such as the refrigeration circuit, electrical control and illumination circuits but sufficient details are given to explain the concept of the present invention.

The cabinet illustrated comprises a base 10, a rear wall 12, a top wall 14 and not shown endwalls. The front 1 8 is open to allow access by members of the public to a base tray 20, and two product shelves 22 and 24. The cabinet is constructed so as to provide two air flow circuits, referred to herein as a primary and a secondary.

The primary air flow circuit is illustrated by arrows with double heads whilst the secondary is illustrated by arrows with single heads. Inside the base 10 is a fan 26 which blows air over an evaporator coil 28 of the refrigeration circuit, and the air passing over the coil 28 is deflected into a channel 32 in the rear of the cabinet. The channel 32 leads some of the air passing therethrough to the channel 34 in the top wall and then to a honeycomb outlet 36 from which the air issues.

The air issuing from outlet 36 passes in a curtain 38 to an air grille inlet 40 at the front edge of the base 10, and the incoming air passing through inlet 40 is then picked up by fan 26 and recirculated over the coil 28.

Conventionally, some of the air which passes through channel 32 passes through a perforated screen 42 extending for the height of the interior of the cabinet, and passes through in an evenly distributed fashion as indicated by the arrows 44.

This air has a tendency simply to exude from the screen 42 and tumble into the base of the refrigerated space, and it is eventually drawn in through the inlet 40 and is recycled. Although this arrangement works satisfactorily in refrigerated cabinets of which the space is to be cooled down to a temperature of the order of OOC when it is required to cool the products say down to a temperature of --100C, when the cabinet is to hold frozen meat, operating the cabinet in the manner described above results in moisture being extracted from the atmosphere to such an extent as to cause condensation and freezing of water on the metallic surfaces of the shelves 22 and 24 and other parts of the interior of the cabinet.The invention aims at overcoming this disadvantage and by a simple modification achieves an internal cabinet space temperature of the order of 00C which is desirable for frozen meat, without the frosting or the same extent of frosting as in the usual arrangement.

In accordance with the illustrated embodiment of the invention, additional deflectors 46, 48 and 50 are provided, and each of these deflectors causes the air flowing through the perforated screen 42 adjacent thereto to be channelled upwardly and then outwardly as indicated by the arrows 52, 54 and 56, so that the deflected air issues from outlets 58, 60 and 62 in downward streams, parallel to the curtain 38, so much so that eddy currents 64, 66 and 68 are set up above the base shelf 20 and the said shelves 22 and 24, and these currents maintain the cabinet space above the surfaces cool and moisture free down to a temperature of the order of --100C.

The outside curtain 38 assists in maintaining the eddy currents and also of course serves to isolate the cabinet space from the surrounding atmosphere. The rear sides of the plates 46, 48 and 50 are preferbaly provided with insulating back panels 51 as indicated by dotted lines.

In order to separate the primary and secondary air flows soon after the air passes over the evaporator 28, the rear passage may be provided with a dividing partition 30 as indicated in dotted lines, forming an outer passage 32A through which all of the primary air flows and which connects with passage 34, and an inner air passage 32B through which all of the secondary air flows and from which all of the air is forced through plate 44.

With this embodiment of the invention described, results are improved further if a larger fan, giving more air flow, and a larger evaporator is used.

As mentioned herein it is possible to provide a different structural design for the cabinet as required.

Claims (4)

Claims

1. A refrigerated display cabinet of the type to which access is gained through an open front, and in which there is an air circulation cooling system to keep the contents cool, such air circulation cooling system providing an air curtain across said open front to insulate the cabinet interior from the atmosphere, and also including means to cause issuance of air from a perforated rear wall of the cabinet into the cabinet interior space over a support surface for goods to be contained in the cabinet, said cabinet including deflection means to deflect the air issuing from said rear wall upwardly then outwardly over the said space to meet the said air curtain and cause the creation of eddy currents in the said space.

2. A display cabinet according to Claim 1, wherein the cabinet has several of said support surfaces defined by the cabinet floor and/or one or more shelves in the cabinet, each said space being defined by the surface and a shelf or a top of the cabinet located thereabove, and there is a deflection means associated with each support surface.

3. A cabinet according to Claim 1 or 2, wherein the or each deflection means includes a deflector plate having an upright portion adjacent the rear wall and a substantially horizontal portion extending forwardly from the top of the upright portion, the deflector place with the rear wall and an overhead shelf or a top of the cabinet forming a passage along which the air issuing from the rear wall is directed.

4. A refrigerated display cabinet substantially as hereinbefore described with reference to the accompanying drawings.