USE OF HEAT IN COLD STORAGE APPLIANCES |
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申请号 | EP02704976.6 | 申请日 | 2002-03-13 | 公开(公告)号 | EP1368601B1 | 公开(公告)日 | 2009-02-25 |
申请人 | Applied Design and Engineering Limited; | 发明人 | WOOD, Ian, David; | ||||
摘要 | |||||||
权利要求 | |||||||
说明书全文 | This invention relates to the art of cold storage, including appliances such as refrigerators and freezers for storing foodstuffs and other perishables. Other applications of the invention include storage of chemicals and medical or biological specimens. The invention also finds use in mobile applications, for example in the transport and storage of perishable goods. The invention develops and adds to the various features of the Applicant's co-pending International Patent Application No. Briefly to recap the introduction of The invention herein and the inventions in A cooler unit generates a convection loop within the cabinet, in which air cooled by the cooler unit sinks toward the bottom of the cabinet and as that air absorbs heat during its downward journey, it warms and rises back up to the cooler unit where it is cooled again. It is also possible to have forced-air circulation by means of a fan within or communicating with the cabinet. The shelves or drawers are typically made of wire so that they offer little resistance to this circulation of air. Upright refrigerators and freezers are often combined and sold as a single-cabinet 'fridge freezer' unit with a refrigerator occupying an upper compartment and the freezer occupying a lower compartment, or vice versa. As different temperatures are required for the two compartments, they are partitioned by a solid divide and each compartment has its own door and cooler unit, conventionally in the form of an evaporator. The domestic fridge freezer usually has only one compressor and the refrigerator evaporator is in series with the freezer evaporator. In that case, temperature control and measurement is usually confined to the refrigerator compartment. Where temperature control is required in both compartments, the evaporators are in parallel and have respective solenoid valves and temperature switches providing on/off cooling mass control to each compartment. In either case, however, the temperature within the respective compartments cannot be duplicated: one compartment is for chilling, so it has less insulation than the other and its temperature can be adjusted within a range above zero Celsius, and the other is for freezing, so it has more insulation than the other and its temperature can be adjusted (if at all) within a range below zero Celsius. Neither compartment can do the job of the other. In upright-door arrangements, the limitations of the vertical seal mean that loss of cold air and induction of warm air can even occur when the door is closed. Being denser than warmer air, the coldest air collects at the bottom of the cabinet and applies pressure to the sealing interface so that unless the seal forms a perfect seal between the door and the cabinet, that air will escape. The present invention and Finally, the present invention and Conventional cold-storage appliances exemplified by upright refrigerators and chest freezers are not the only prior art disclosures of interest. For example, it has been known for many years to divide a refrigerator into compartments, each with its own dedicated door or lid. Examples of this idea are disclosed in UK Patent Nos. In those Earle documents, the front of the cabinet is provided with a plurality of rectangular openings for receiving drawers. Each drawer has a front panel larger than its respective opening so that a vertical seal is formed around the overlap when the drawer is in a closed position. The drawers and their contents are cooled by a cooler unit that circulates cooled air by convection within the cabinet, in common with the types of refrigerator already described. To promote circulation of this air amongst all of the drawers, the drawers are open-topped and have apertures in their bottoms. Also, the drawers are disposed in a stepped arrangement, those at the top of the refrigerator extending back less far into the cabinet than the lower drawers so that the rear of each drawer is exposed to the downward flow of cooled air from the cooler unit. Although only one drawer need be opened at a time, the apertures in the bottom allow cold air to flow freely from the open drawer, which is replaced by warm moist ambient air to the detriment of energy efficiency and with the increased possibility of cross-contamination. Indeed, when a drawer is opened, cold air within the cabinet above the level of that drawer will flood out, drawing ambient air into the cabinet. Furthermore, the drawers encourage ambient air to flow into the interior of the refrigerator because, upon opening, they act as pistons drawing the ambient air into the interior of the refrigerator cabinet. Once in the cabinet, the warm air can circulate as freely as the cold air that is supposed to be there. Even when closed, the accumulation of cold air towards the bottom of the cabinet will exert increased pressure on the vertical seals of the lowest drawers, increasing the likelihood of leakage if the seal is faulty. A further example of the above type of refrigerator according to the preamble of claim 1 is disclosed in UK Patent No. Very little detail is given about the seal that is formed between the drawer and the horizontal member, other than that the horizontal member has a downwardly projecting rear end with a biased edge that makes a close fit with the rear wall of the drawer. Nothing else is said about the junction between the drawer and the horizontal member, apart from the general statement that the drawer is adapted when in its closed position to fit 'fairly snugly' against the horizontal member. It can only be inferred that the drawer and the horizontal member merely abut against each other. Whilst this will impede the passage of air into and out of the drawer, it will not form an impervious seal. As this is not a vapour seal, icing and cross-contamination is likely to occur even when the drawer is closed. The drawer arrangement described creates a compartment in which a different temperature can be set when compared to the essentially common temperature of the rest of the refrigerator. It is particularly envisaged that the drawer can act as a freezer compartment. The Applicant has appreciated a disadvantage in this arrangement, namely that as the freezer drawer resides within the cooled interior when closed, the outer surfaces of the drawer within the cabinet will be cooled to the temperature of the refrigerator. Accordingly, when the drawer is opened, those cooled outer surfaces will be exposed to ambient air containing moisture that will condense on the cooled surfaces leading to an undesirable accumulation of moisture. Condensation involves transfer of latent heat from water vapour to the drawer, thus increasing the burden of cooling the drawer again when the drawer is returned to the closed position within the cabinet. Additionally, condensed moisture will be transferred to the interior of the refrigerator when the drawer is closed. As discussed above, the presence of water promotes microbial activity. A further disadvantage of introducing water into the interior of the refrigerator is that it may freeze: this can be a particular problem where the drawer of the enclosed compartment meets the insulated top, as any ice formation will form a seal that locks the drawer in a permanently closed position. In fact, the of ice formation is due to moisture migration across the interface between the drawer and the top. This disadvantage was appreciated by Earle, as a cam mechanism is mentioned in A further interesting prior art document, cited as technological background against That aside, the spillage of cold air in Ewen lowers the temperature within the cabinet around the drawers, and so increases the likelihood of condensation on the drawers when opened. It will be noted that cold air spilled in this way can fall freely behind the drawers within the cabinet and so expose the exterior of the drawers to air substantially below ambient temperature. Certain design details of Ewen worsen this effect. For example, the bottom wall of the Ewen unit is an efficient insulator which will significantly reduce the surface temperature of the drawers. Also, the internal divisions between the drawers do not allow for ambient heat transfer to the drawers but only for heat transfer between the drawers, thus promoting drawer-to-drawer temperature equalisation over time. Left for long periods, or even overnight, large parts of the external surface of each drawer will fall to temperatures significantly below ambient dew point. Condensation or ice will therefore form on those surfaces as soon as the drawers are opened; similarly, if the drawers are removed and left outside the appliance, they will start to 'sweat' with condensation. Like Earle, opening and closing a drawer within a sealed cabinet in Ewen acts like a piston, alternately applying both negative and positive pressures to adjacent areas. This promotes air transfer through the drawer opening at the front of the cabinet, which can displace cold treated air in a drawer, and within the cabinet itself. An over-sized cabinet would reduce the piston effect but would also be wasteful of space. Conversely, a more space-efficient close-fitting cabinet may decrease the displacement of cold treated air, and so reduce the burden of cooling the warmer air that takes its place, but it will increase resistance to opening and closing the drawer. Cold air spillage aside, the gap inevitably left between a drawer and its associated lid in prior art arrangements is large enough to allow the passage of enzymes, spores and other airborne contaminants. Also, Ewen discloses a common interconnecting drain and this too would allow free transfer of contaminants between each drawer, particularly under the aforementioned piston action. Whilst Ewen speaks of different temperatures in different drawers, the plurality of cooling lids are connected in series and have no means for individual temperature control in each drawer. The different temperatures are designed-in by providing some drawers with more cooling elements than others, but there is no measurement or control of those temperatures in use. Also, like the compartments of more conventional prior art, each drawer in Ewen has a fixed function, namely freezer or refrigerator. Even if removed from the appliance, Ewen's drawers will stay attached to their drawer fronts and runners. This does not lend the drawers to temporary storage or transport. Moreover, like Earle, the drawers in Ewen cannot be opened fully: they can only be opened less than half-way while being supported by the structure of the appliance. This is to the detriment of access to, and visibility and illumination of, the contents. It is against this background that the present invention has been devised. The invention resides in a cold-storage appliance including the features set out in Claim 1. In order that the present invention can be more readily understood, reference will now be made, by way of example only, to the accompanying drawings in which:
The drawers 4 can be slid horizontally into and out of the cabinet 6 by means of tracks or runners on the sides of the drawers 4 that will be described in more detail below. If there is no back panel 14, it is theoretically possible for a drawer 4 to be removed from the cabinet 6 in more than one direction, as shown in Each drawer 4 comprises an insulated open-topped bucket-like container 16, at least one container 16 (in this case, that of the central drawer 4) being of a different depth to the other containers 16 to defme a different internal volume. These containers 16 will be referred to in this specific description as storage bins or more simply as bins 16. The bottom bin 16 leaves only a narrow gap to the bottom panel 10 of the cabinet 6, whereas the top bin 16 leaves a substantial space at the top of the appliance 2 under the top panel 8, allowing room for a compartment 18 that accommodates a refrigerator engine 20, for example including condenser and compressor means as is well known. The relatively deep bin 16 of central drawer 4 is intended to hold bottles and other relatively tall items stored upright, whereas the other, relatively shallow bins 16 are for correspondingly shallower items. Compared to the shelves and other compartments defining the main storage volume of a conventional upright cold-storage appliance, all of the bins 16 have a favourable aspect ratio in terms of the substantial width of the access opening compared to the depth of the compartment thereby accessed. It is therefore very easy to reach every part of the interior of a bin 16 when a drawer 4 is opened. The interior of the cabinet 6 is divided by five insulated lids 22, one for each drawer 4, that are generally planar and horizontally disposed. When a drawer 4 is closed, the open top of its associated bin 16 is closed by an appropriate one of the lids 22 in a manner to be described. The lids 22 include cooling means 24 being evaporator elements of known type disposed in the lower face 26 of each lid 22 to cool the contents of a bin 16 closed by that lid 22. Each bin 16 has a generally flat front face 28 that is exposed when the drawer 4 is closed. The front face 28 could be provided with a decorative panel as is well known. When the drawer 4 is closed, the front face 28 of the bin 16 is bordered at the top by a control and display panel 30 dedicated to that bin 16, the panel 30 being co-planar with the front face 28. The panel 30 is supported by the front edge 32 of the appropriate lid 22, the panel 30 being recessed into the front edge 32 of the lid 22. The control and display panel 30 contains a number of displays, switches and audible alarms, thus providing a user interface for each bin 16. For example, the interface will most commonly be used for selecting the temperature to which the bin 16 is to be cooled, but also contains temperature displays, on/off and fast-freeze switches, a light indicating when the drawer 4 is open and an audible alarm to indicate when the drawer 4 has been open longer than a predetermined time or when the temperature inside the bin 16 has reached an upper or lower threshold. A rounded handle 34 extends across substantially the entire width of the top portion of the front face 28 to enable the drawer 4 to be pulled out when access to the interior of the bin 16 is required. The bottom of the front face 28 of each bin 16 is bordered by a slot 36 that, as will be described, admits ambient air into the cabinet 6. To do so, each slot 36 communicates with an air gap 38 extending beneath the entire bottom face 40 of the associated bin 16 to meet a void 42 maintained behind each bin 16, the void 42 being defined by the inner surfaces of the back 14 and side 12 panels of the cabinet 6 and the backs 44 of the bins 16. As can be seen particularly from The air gaps 38 beneath the bins 16 and the void 42 behind the bins 16 also communicate with air gaps 38 to the sides 48 of the bins 16. Optionally, vents 46 are provided in the side panels 12 of the cabinet 6 adjacent to the bins 16 through which ambient air can also be admitted. As best illustrated in It will be noted that the piston action created by opening a drawer 4 that sucks ambient air into the interior of the appliance 2 does not pose a problem in this invention. In fact, this action is advantageous as it promotes circulation of ambient air within the cabinet 6. Accordingly, ambient air entering the cabinet 6 through the front slots 36 and, if provided, the side vents 46, leaves the cabinet 6 through the apertures 56 provided in the front face 52 of the refrigerator engine compartment 18, and so ambient air is circulated through the cabinet 6. More specifically, ambient air enters the appliance 2 where it immediately comes into contact with the outer surfaces 40, 44, 48 of the bins 16 and warms them to ambient temperature (or substantially so, as a surface resistance effect means that a sub-ambient boundary layer will remain due to the temperature gradient across the thickness of the bin wall) before being drawn towards the void 42 and then upwards through the void 42 by the circulation of the air. The arrows of By exposing the external surfaces 28, 40, 44, 48 of the bin 16 to warmer air than it contains, there is no problem with condensation on the external surfaces 28, 40, 44, 48, and hence no problem with latent heat transfer to the bin 16 or the icing and cross-contamination difficulties of condensed water entering the cabinet 6. In any event, cross-contamination would be unlikely to occur because each bin 16 is tightly sealed when its drawer 4 is closed. So, even if microbes enter the cabinet 6, they cannot readily gain access to other bins 16. It is also unlikely that two bins 16 would be open together at any given time. It would be possible to include means for enforcing this, for example using a mechanism akin to that used in filing cabinets for anti-tilt purposes, by preventing more than one drawer 4 being opened at a time. Such a mechanism will be described later. When a bin 16 is open, its open top does not suffer much spillage of cold air, and when a bin 16 is closed, the horizontal seals 60 are inherently better at sealing-in cold air than the vertical seals commonly used in upright refrigerators and freezers. Whilst horizontal seals are known in chest freezers, this invention does not suffer the inconvenience and space problems of chest freezers, instead being akin in those respects to the much more popular upright appliances. The seals 60 can have magnetic qualities, for example being operable by permanent magnets or electromagnets, or may employ hydraulics or pneumatics to expand or contract them. As there has to be a large temperature gradient between the cooled inner surfaces 62 of each bin 16 and its outer surfaces 28, 40, 44, 48, the bins 16 are constructed from an efficient insulating material so that the gradient is easily maintained with the outer surfaces 28, 40, 44, 48 remaining close to the ambient temperature. Materials such as phenolic foam or polyurethane foam (optionally skinned with GRP or a polycarbonate in a composite structure) are particularly preferred for the construction of the bins 16. If segregation of the contents of a particular bin 16 is required, that bin 16 may be fitted with removable inserts 64. The inserts 64 are of varying shape and dimensions and may be used to define many types of compartments. For instance, an insert 64 may be a thin partition with a length corresponding to the length or width of the bin 16 in which it is received. An insert 64 may be a box, with or without a lid, or an insert 64 may include clips for holding bottles in place or trays for holding eggs or the like. An insert 64 could also be a wire basket or shelf. As can be seen in It is also possible for a transport cover 66 to include a refrigerator engine powered internally by batteries or a gas supply or externally by mains electricity or a vehicle electricity supply. Although not shown in the general views of As best appreciated from Apart from the vertical array of drawers 4 common to the embodiments described above, a side-by-side arrangement of drawers 4 is also contemplated as shown in The depth of the drawers 4 is maximised within the limited available height by mounting the refrigerator engine 272 and control panel 274 in a side-slung position to one side of the appliance 268 as shown. Also, the side view of Referring now to However, like Ewen and unlike the preceding embodiments, there is no provision for vertical movement of the bin 16 with respect to the lid 22: instead, the bin 16 simply slides horizontally past the close-fitting lid 22. The gap between the bin 16 and the lid 22 that is therefore necessary requires the creation of a complete external vapour barrier around the compartment that houses each drawer, so as to overcome the associated moisture transmission and cross-contamination problems. Thus, as Ideally, the walls of each drawer compartment should be of a thin, poorly-insulating material with all of the external surfaces exposed to ambient air. That ideal is not practically achievable, although use of a thin material that conducts heat from outside the drawer compartment and promotes convection of heat within the drawer compartment is to be encouraged. In reality, a temperature gradient will form over time inside the sealed compartments due to the insulating effect of the external enclosure and the air cavity around the bin 16, coupled with the refrigerating effect of the gap between the bin 16 and the lid 22. Additionally, an insulation trap will occur where external surfaces of a compartment are adjacent to other compartments. This further cools the air around the bin 16 and so increases the temperature gradient. For this reason, The idea of warming the external surfaces of the bin 16 within a drawer compartment is expanded upon in The central supply air duct 388 is aligned with the tangential fan 382 which is generally cylindrical and spins about a horizontal axis near the top of the casing 386, powered by a motor 392. As the fan 382 does so, it impels cold air out of the casing 386 through the central supply air duct 388 and into the bin 16 via ducts (not shown) in the lid 22. A cooling coil 394 is supported within the casing 386 immediately beneath the fan 382, in such manner that gaps are left beyond the ends of the coil 394 beneath the return air ducts 390. The cooling coil 394 comprises a serpentine finned element through which relatively warm air rises, drawn by the fan 382, and by which that air is cooled before being impelled by the fan 382 into the bin 16. The relatively warm air is that which is drawn into the casing 386 from the bin 16 through the return air ducts 390. Whilst the solutions described in The invention has wide-ranging applications and benefits for storing, handling, distributing, transporting and delivering items in the right condition, notably:
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