IMPROVEMENT IN TEMPERATURE MONITORING

Abstract: A rigid polymeric matt-finish box, of rectangular shape and size generally resembling a package of chilled foodstuff, contains internally a block of iron (15) wrapped in elastomeric foam portions (16), as a heat-sink responsive to temperature of the surrounding air, and arising from incident radiation, in generally the same manner as a typically cook-chill foodstuff i.e. cooked chicken portions. Temperature sensor (17) is read at intervals controlled by time-interval sampling means (18) and these temperature data are stored electronically at (19). Computational unit (20) operates jointly, on temperature sampled and on a measured period of sampling, to indicate alarm conditions externally at (12), the other external light (13) being responsive to low-battery conditions at battery B. Interrogatable output means (22) are located behind glazed window (14) so that selectively an external interrogation unit, itself also with a glazed window, can be hand-held with the respective windows adjacent to actuate by a beam of I.R. light the interrogatable output means (22) and to transfer stored data at (19) out through window (14) to the external interrogation unit, for onward transfer or printout.

Description: IMPROVEMENT IN TEMPERATURE MONITORING This invention relates to the monitoring of temperature in a controlled temperature enclosure which is subject to occasional temperature-disturbing effects disturbing its contents. More especially it relates to monitoring of the temperature at any point within an open-fronted chill cabinet utilizing circulated cold air and provided for the display of and access to chilled foodstuffs. In recent years cooked and chilled convenience foods have found considerable market acceptability. Such foodstuffs are centrally cooked, reduced rapidly in temperature without freezing, and transported in a chilled form in suitable temperature-controlled road vehicles to display cabinets at the retail outlets. A typical display cabinet is a tall chest with insulated walls and an open front. It carries in the base part or all of a refrigerating unit providing cold air. The inlets for this air are in the base of the cabinet, and the air is reduced to the necessary temperature, pumped through ducting up within the back of the cabinet, and allowed to spill outwards and forwards from vents at the back and at the top. The downward passage of the colde air encounters articles on the shelves so that the cold air is distributed in its passage over all of the shelves and down again to the base for recirculating. In practice, the design of the cabinet can be such that only a minimum of cold air escapes into the surrounding and so that the contents are held at a nominal temperature of for example 5°C with immediate access fo the customer. However, customer access and handling of the product (which can be held in metal trays with a cardboard sleeve, but can also be otherwise presented) disturbs the even movement of air and leads to some cold air los and warm air incursion into the cabinet. Over the year it has become known that the temperature of a cabinet, although nominally 5°C, can be rather increased down th front of the cabinet and in pockets extending inwards along the side walls. To ensure that the foodstuff does not reach unacceptabl high temperatures, which could lead to growth of bacteria such as salmonella it is known to check the temperature by positioning a thermometer or thermometer either permanently or successively at different locations within the cabinet. For convenience, the locations of particular risk are usually chosen. The temperature of the thermometer is noted at intervals a a guide to the refrigeration condition of the cabinet and the quality of the contained foodstuffs. In practice, this can lead to a number of problems. Firstly, the thermometers can become dislodged or broke especially if they are of the glass-bulb mercury or alcohol type. Secondly, the retail staff must remember to take readings at frequent, and if possible regular, intervals and may in future, to comply with regulations need to preserve those readings in a uniform manner. A possible solution involving the use of an associated notebook kept in or near the cabinet would be accordingly liable to loss, damage or misuse. Moreover, the data entered into such a notebook would not be secure against any alteration or fictitious retrospective entries. A rather different danger arises if the observations and recording are subject to very strict managerial control. Conscientous staff, observing that a thermometer reading is in excess of an upper limit, may decide to withdraw from sale all of the material in the cabinet, with consequent loss, even though the high reading may be purely transient. Operational difficulties are exacerbated by proposed legislation which will impose maximum temperatures at which such foods intended for sale must be kept, and in practice will make it mandatory to keep a record of temperature within such cabinets, in a form which can b inspected by authorities at random intervals. The present invention sets out to provide equipment for monitoring temperature within an at least partially enclosed temperature-controlled container susceptible to temperature-influencing access to articles within th container. In one aspect the invention consists in a temperature recording and monitoring device for articles located within a temperature-controlled enclosure and liable to individual retrieval from the enclosure, comprising a housing containing thermal performance components and temperature recording components; the surface and composition of the housing, and the mass and nature of the thermal performance components being such as to mimic the temperature changes in a typical one of said articles engendered by contacting air or absorbed radiation; and temperature recording component comprising means for retrieving at intervals data relative to temperature of the thermal performance components, means to store such data, and means to transmit such data during external interrogation. The temperature recording and monitoring device defined above is therefore particularly valuable for recording and monitoring temperatures within a vertical open-fronted chill-cabinet through which cold air is circulated from vents at the top. The housing of the device is typically of a straight sided box nature, which can comprise, for example, a suitably matt or coloured generally rigid synthetic polymer. The thermal performance components will tend to comprise a heat sink, eg in the form of a lump of metal, and surrounding thermally insulating layers such as a layer or layers of elastomeric foam. The box may be of a size generally to resemble the size of a tray of cooked chilled foodstuffs, for example chicken pieces, and should be of the same thermal performance under cabinet conditions. The temperature recording components are typically connected to the metallic heat sink of the thermal performance components, and are electrical in nature. The readings can be fed to a conventional electronic memory store, for occasional retrieval from outside of the housing. While this retrieval can be done by plugging in a lead to an external device, it is preferred within this form of the invention to provide a glazed window such that an interrogatable component beneath the window can both be actuated by and reflect an infra red beam from outside, thereby facilitating transfer without trailing wires to a suitable hand-held external unit. The space within the housing preferably further comprises electrical circuitry such as to provide, from the data, computation such as to record a coefficient derived from any excess temperature reading and the tim of excess, said computational circuit being connected t an alarm system, for example, an externally visible light alarm for actuation if a predetermined computational limit is exceeded. It is also within the scope of the invention to provide an externally visible light alarm for a low battery condition. The invention further extends to the combination of a plurality of devices as defined above with one or more interrogation devices which can be selectively utilized to retrieve data from each temperature recording and monitoring device. The invention further extends to a method of temperatur recording and monitoring for articles located within a temperature controlled enclosure, in which the device a defined above is placed from time to time at different positions within the enclosure and the accumulated data relevant to internal temperature of the device is retrieved at intervals utilising a suitable interrogation means. The invention will be further described with reference to the accompanying drawings, in which: Figure 1 shows diagramatically a typical display cabinet for chilled cooked food, the cabinet including a temperature recording and monitoring device according to the invention. Figure 2 shows diagramatically the exterior of such a temperature recording and monitoring device. Figure 3 shows diagramatically the essential features on the interior of the device of Figure 2. Figure 4 shows a hand-held data retrieving device to retrieve the information from the temperature recording and monitoring device as a permanent record. The cabinet 1 shown in Figure 1 is of conventional form. It comprises a base region 2, upstanding glazed vertical insulated walls 3, a succession of polymer coated or painted shelves 4 held between the walls 3, and an insulated top 5. Within the base is part or all of a standard refrigeration unit (not shown) , and extending upwardly within the back wall 6, is cold air ducting (also not shown) fed by the refrigeration unit. This ducting distributes chilled air to holes 7 at the back of the cabinet, from which the air flows forwardly and at least in part re-enters air inlet holes 8. There will of course be temperature controls governing the temperature of the air itself. As will be apparent from Figure 1, there is an interface with warmer ambient air at the open front of the cabinet. We have established that there is a danger of penetration of warm air inwards at the sides of the cabinet and to some extent inwards at the top of the cabinet. These represent the danger areas therefore for storage of materials. The materials 9 stored on the shelves can be any of a wide range of cook-chill foodstuffs. A major proportio of these are based upon chicken portions cooked in various styles and chilled so that they merely need to re-heated, without loss of flavour as might occur in th case of deep-frozen foodstuffs. Pieces of cooked chicken are of fairly thick dimensions for foodstuffs and are susceptible to consumer fears of growth of bacteria. In many respects they represent the most taxing of materials to display on a cook-chill basis. They have therefore been used to define the parameters of the present invention. The present invention is based at least in part upon the realisation that a more accurate indication of received temperature on a pack of foodstuffs can be ascertained not merely by measuring the temperature of the contacting air but by measuring the whole body temperature of the foodstuffs. This temperature is a consequence of all of the heat absorbed by the foodstuffs under given conditions. Thus, as well as contact with the air, so that the foodstuff is chilled by convection or conduction, there is an appreciable element of absorbtion of energy from the surroundings. The lights in the stores, and in the cabinet itself, provide radiant energy and this is absorbed by the package 9 of foodstuff and converted to heat. This absorbtion is however dependent upon the temperature of the emitting source and also upon any reflected or absorbtive areas in the packaging, together with the internal composition of the package 9 and its behaviour under fluctuating absorbtion of energy. The temperature recording and monitoring device according to the invention is accordingly configured typically as shown at Figures 2 and 3, rather than being a simple bulb (or electronic) thermometer sensor responsive only to the cold air. As shown in Figure 2, the external appearance of the temperature recorder and monitor is that of a straight sided box 10. In a typical embodiment, the box 10 is made of more or less rigid synthetic polymer with a mat finish and a neutral greyish colour. The exterior of the box is provided with two small alarm lights 12, 13, and a glazed window 14. The box 10 is used by placing it from time to time in different places within the cabinet 1, especially in those places most subject to the risk of temperature fluctuation. Since, as described below, the lights are alarm lights the device is preferably placed with the lights 12, 13 facing forwards. Figure 3 shows diagramatically the essential features o the interior of the box 10. Firstly, there are the thermal features. In the embodiment shown, the essential thermal sink of the box is a cube or block of iron 15, perhaps 2 or 3cms in its length, wrapped in a layer of elastomeric foam 16 which is of the order of 1cm in thickness. This combination is located between the walls of the box 10 as a predominant heat absorbing structure with a close resemblance, in its heat absorbing and temperature change characteristics, to a typical cook-chilled meal of chicken pieces. The effect of this is therefore tha the temperature recording and monitoring device fluctuates in temperature within the cabinet in the same way as such a packaged foodstuffs having regard to the cold air temperature and the absorbtion of other energies from store lighting or cabinet lighting, etc. The device 10 shown clearly needs to have a volume and a surface typical for the stated temperature behaviour. This volume facilitates storage within the box of other components which, without affecting the temperature characteristics, are of considerable value in its operation. Thus, shown diagramatically, there is a battery 13, a temperature sensor 17 responsive to the temperature of the metal block 15 itself, means 18 for operating the sensor at intervals, and preferably at regular intervals; means 19 for recording the temperature thereby measured, in the form of a readable memory store; computational means 20 for taking a measure of excess temperature and a measure of elapsed time and deriving jointly from them a coefficient of acceptability of performance; circuitry whereby an excess value of said computation operates one of the lights 12 at the exterior of the casing; means responsive to a low output from the battery to operate the other of the alarm lights 13 and thereby indicate the need for battery change; and interrogatable output means 22 behind the glazed window 14 for said temperature values held in memory. In the above it will be clear that the device samples temperature, (17, 18) and stores the sample value in a memory for as long as may be required. Additionally, i performs a computation (20) upon the sampled value, usually only if such volume is in excess of a predetermined upper temperature range. Transient excesses of temperature are acceptable but, if the excess temperature, and the time over which the excess persists, jointly multiply to a coefficient of performance acceptability outside a predetermined value then the alarm light is triggered. If desired, the device as shown could be taken out each evening and interrogated by management staff so as to give a daily record of the cabinet performance. Alternatively, it could be interrogated whenever required so that the information in the memory can be retrieved and for example converted to a print-out of numerical values of temperature or as a graphical representation of such temperature. Figure 4 shows a hand-held device which can be used for such interrogation. It is again in the form of a box 3 of synthetic polymeric material the most important feature of which is a glazed window which can be put adjacent to the glazed window 31 of the temperature recording device (or, if desired, left at some distance from that glazed window) and subject to an infra red beam generated from within the hand-held recorder. The infra red beam traverses the glazed windows 31, 14, actuates the interrogatable means 22, and by reflection carries the information within the memory of the temperature recording and monitoring device into a memory of the hand-held device 30. This information in the hand-held device can be used to operate a suitable numerical or graphical print-out 32 as and when desired. Thus, the frequency and regularity of measurement is not dependent upon the conscientiousness of staff; the decision to dump the contents of the cabinet is taken on a rational time-temperature coefficient rather than an ad hoc transient temperature figure; a permanent record as now required by regulation is provided; the record can be interrogated without physically touching the device or otherwise altering its activity; and the device is caused to operate upon the more accurate concept of "whole body" recording of temperature as distinct from the recording of the temperature in the contacting cooled air only. Various modifications may be made to the device as shown above. For example, what is shown in relation to a retail open-fronted cook-chill cabinet device or similar devices could be used in any temperature controlled enclosure, whether in the food industry or otherwise, wherein the temperature conditions of the wholebody of an article needs to be monitored closely against spoilage.

Claims: CLAIMS 1. A temperature recording and monitoring device for articles located within a temperature-controlled enclosure and liable to individual retrieval from the enclosure, comprising a housing containing thermal performance components and temperature recording components: the surface and composition of the housing, and the mass and nature of the thermal performance components being such as to minimise the temperature changes in a typical one of said article, engendered by contacting air or absorbed radiation; and the temperature recording components comprising means for retrieving at intervals data relative to temperature of the thermal performance components, means to store such data, and means to transmit such data to external interrogation. 2. A device as claimed in claim 1 which has a housing in the form of a straight-sided generally rigid box of matt finish polymeric material. 3. A device as claimed in claim 1 or 2 in which the thermal performance components comprise a heat sink surrounded by a thermally insulating layer or layers. 4. A device as claimed in claim 4 in which the heat sink is a lump of metal and the thermally insulating layer or layers are composed of an elastomeric foam. 5. A device as claimed in any one preceding claim in which the temperature recording components are electrical in nature and give electrical readings which are fed to an electronic memory constituting said data store. 6. A device as claimed in cloaim 5 in which housing includes a glazed window over an interrogatable component, for actuation to a beam of radiation passing through the glazed window and for reflection of information corresponding to the stored data out throug the window after actuation. 7. A device as claimed in claim 6 in which the interrogatable component is actuated by an infra-red beam. 8. The combination of a plurality of temperature recording and monitoring devices as claimed in claim 6 or 7 and an interrogating device for generating an actuating beam to pass in through the glazed window and for receiving information corresponding to the stored data, passing out from the glazed window, whereby it ma be selectively utilized to retrieve data from each such temperature recording and monitoring device. 9. A method of temperature recording and monitoring for articles located within a temperature-controlled enclosure, in which the device as claimed in any one of claims 1 to 7 is placed from time to time at different positions within the enclosure and the accumulated data relevant to internal temperature of the device is retrieved at intervals utilising a suitable interrogation means.

Inventors: GREGORY NOEL, HAY FRANK S, STEWART DOUGLAS, GREGORY, NOEL, HAY, FRANK, S., STEWART, DOUGLAS
Applicants: MARKS SPENCER PLC, MARKS AND SPENCER PLC
Application year: 1991
Main classification: G01K13
IPC codes: G01K1, G01K13