WO2004092697A1

WO2004092697A1 - A temperature indicator, a package for goods and a method of monitoring the freshness of goods kept in packages

Info

Publication number: WO2004092697A1
Application number: PCT/SE2004/000503
Authority: WO
Inventors: Henry Norrby
Original assignee: NYGÅRDH, Mats
Priority date: 2003-04-16
Filing date: 2004-04-15
Publication date: 2004-10-28

Abstract

In a first aspect, the invention relates to a temperature indicator for packages intended for keeping goods in a preservative state in which the temperature must not exceed a certain limit value. The temperature indicator comprises a porous, capillary sucking means (11), as well as at least one liquid (10) by means of which the porous means is wettable with the purpose of triggering a visualization of the ambient temperature having exceeded the limit value. According to the invention, the liquid (10) consists of a liquid, e.g. oil, which has semiplastic consistency at temperatures below said limit value, but becomes liquid at temperatures above the same in order to flow out in the porous means. Furthermore, the invention relates to a package for goods as well as a method of monitoring the freshness of goods kept in packages.

Description

A TEMPERATURE INDICATOR, A PACKAGE FOR GOODS AND A METHOD FOR MONITORING THE FRESHNESS OF GOODS KEPT IN PACKAGES

Technical Field of the Invention In a first aspect, this invention relates to a temperature indicator for packages intended for keeping goods in a preservative state in which the temperature must not exceed a certain limit value, the indicator comprising a porous, capillary sucking means, as well as at least one liquid, by means of which the porous means is wettable with the purpose of triggering a visualization of the ambient temperature having exceeded the limit value.

General Background of the Invention In the food sector not only deep-frozen goods, such as fish, long-term stored meat, ice cream, potato products, etc, are kept and handled, but also chilled goods, such as short-term stored vegetables, fresh meat, fresh fruit, etc. Between said two storage methods, certain fundamental differ- ences exist, the most apparent one of which is the temperatures. While deep-frozen goods during the handling thereof from producer to final consumer, should have a temperature of maximum -18 °C, the chilled goods are usually kept at temperatures above 0 °C, e.g. max +4 °C or max +8 °C.

Prior Art

A time and temperature indicator for monitoring the freshness of packaged goods, in particular foods, is previously known and commercially available under the trademark Vitsab® TTI. This known indicator consists of a label, which includes two capsules made from thin plastic film, which define hollow spaces or chambers containing different liquids, which may be mixed together with each other by a communication way being opened between the chambers, the indicator being activated for monitoring the freshness of an article. When this takes place, an enzyme based liquid mixture is formed, the colour of which may be altered depending on the exposure of the label for temperature and time with the purpose of making visible the progressive deterioration of the article via three spaced apart windows in the label. More precisely, the colour change takes place as an integral function of time and temperature so far that a sudden change from an initial colour, e.g. green, to another colour, e.g. yellow, in each win- dow takes longer time when the label/the article is exposed to an even, low temperature, than when the same continuously or intermittently is subjected to higher temperatures. As the quality of the article is deteriorated, the deterioration is indicated in one window after the other. Immediately after activation of the indicator by mixing together the liquids, all three windows show green colour. After a certain time of exposure for certain (maybe varying) temperature states, a first window changes colour from green to yellow. This indicates that the article still is fresh, but that it has to be sold/be used within a certain time. In the next step also a second window "is lit" by the fact that the colour is changed from green to yellow. Still the article on that occasion is regarded as fresh, but should be sold within comparatively short time. In a last step all windows are coloured yellow. The article should on that occasion either be sold immediately or be discarded.

The above-described time and temperature indicator enables per se a general, time and temperature related monitoring of the freshness of, for instance, foods, such as chilled products, so far that the same for the seller as well as the buyer forms a marking of the type "best before". However, the indicator gives no information at all about whether the temperature of the article generally has exceeded a certain limit value or not. Thus, for chilled products, for instance, it is important that they should not at all during a considerable time be exposed to temperatures above +4 °C (at times +8 °C) . Goods in packages provided with the known temperature indicator may temporary (in hours or day) very well be exposed to considerably higher temperatures, e.g. +10 to +20 °C or more, without other consequence than the time up to last day of sale being shortened. Therefore, in practice, it may happen that goods are sold in spite -of them being unfit as a result of exposure to even relatively short temperature tops . Another disadvantage, construction wise and manufacturing wise of the known indicator is that the same requires use of two different, mixable liquids, which should react with each other in order to bring about a liquid mixture which has the desired ability to change colour depending on time and temperature. In practical series manufacturing of the labels, the need for a plurality of different liquids constitutes a complication.

By WO 01/72601 (based on SE 0001069-4) a temperature indicator is previously known, which is especially intended for monitoring the freshness of deep-frozen foods, i.e., goods the temperature of which should not exceed -18°. This temperature indicator makes use of a contrast fluid, which is initially transparent and maintains the transparency thereof dur- ing temperature reduction past a certain desired temperature value, but is converted in an irreversible way to an opaque state, if the temperature should exceed the desired value- Also in this case, two different liquids are required in the manufacture, viz. an initially transparent indicator liquid having a comparatively low freezing point and a phase changing liquid, which has a somewhat higher freezing point and which is contained in a burstable capsule. Upon freezing of the article, said liquids are kept spaced apart via the capsule, but when the liquids freeze and transform into a fixed state of aggregation the capsule bursts. Upon a possible thawing of the article, when the temperature rises above the desired value, the liquids^' return to the liquid state, the phase- changing liquid colours the indicator liquid dark. In a particular embodiment this phenomenon is utilized in such a way that an initially transparent part of the temperature indicator is brought to cover a bar-code, scanning of the bar-code being made .impossible if the temperature indicator .is triggered and making the covering indicator part dark or opaque. Furthermore, an indicator of the type initially men- tioned is previously known by US 3414415. In this case, the indicator is intended for monitoring deep-frozen foods, and uses for this purpose a liquid in the form of a saline solution having a colouring agent, which after priming of the indicator successively may diffuse out in a porous, capillary sucking means, such as a paper strip, the strip gradually being coloured by the liquid. However, like the above-mentioned indicator of the type Vitsab® TTI this indicator constitutes a combined time and temperature indicator, which per se enables a visualization of a progressive deterioration in course of time of the freshness of a deep-frozen article, but which cannot make clear whether either frozen or chilled goods have been exposed to shorter or longer rises in temperature above a set limit value.

Objects and Features of the Invention

In a first aspect, the present invention aims at obviating the abovementioned disadvantages of previously known temperature indicators and at providing an improved tem- perature indicator. Thus, a primary object of the invention is to provide a temperature indicator, which in a simple and reliable way can make clear whether a chilled or deep-frozen article and the package thereof during the handling thereof from manufacturer/seller to consumer at all has been exposed to temperatures above a certain limit value. Yet an object of the invention is to provide a temperature indicator which grants much freedom to the manufacturer to make the indicator with different information messages, e.g. fields or markings having different colours, without because of this complicating the manufacture. Another object of the invention is to provide a temperature indicator, which is suitable for co-operation with barcodes on packages for goods with the ultimate object to integrate the freshness monitoring function of the temperature indicator with computer systems of shops. Furthermore, the temperature indicator should be structurally simple and inexpensive to manufacture in large quantities. Yet an object of the invention is to provide a temperature indicator, which can be manufactured and is kept/transported substantially independently of prevailing temperature states in order to finally be activated or primed for the freshness monitoring purpose thereof first in connection with the application of the indicator on a package or in connection with the package being filled with the contents thereof. According to the invention, at least the primary object is attained by the features defined in the characterizing clause of claim 1. Preferred embodiments of the temperature indicator according to the invention are furthermore defined in the dependent claims 2-12.

In a second aspect, the invention also relates to a package for keeping goods in a preservative state in which the temperature must not exceed a certain limit value. The features of this package are seen in the independent claim 13. An advantageous embodiment of the package according to the invention is further defined in the dependent claim 14.

In a third aspect, the invention also relates to a method for monitoring the freshness of goods kept in packages. The features of this method are seen in the independent claim 15.

Summary of the Invention

The invention is based on the intention to in a temperature indicator provided with a paper strip, or other porous capillary sucking means, use a liquid of the type that has a semiplastic or non liquid consistency at temperatures below a certain limit value, but becomes liquid at temperatures above the same. For chilled goods as well as frozen foods, at least certain vegetable and/or animal oils are suitable. For instance, olive oil alters the viscosity thereof at approximately +4 °C in such a way that the oil is semi- plastic or at the most very viscous at temperatures below +4 °C, but becomes of low viscosity at higher temperatures. According to the invention, this phenomenon may be utilized in such a way that the temperature indicator is primed for the temperature monitoring purpose thereof first in connection with it being in a cold environment, e.g. when the indicator is to be applied to a package for chilled goods. This may take place by a communication way being opened between on one hand, a capsule, in which the liquid is contained, and on the other hand a porous strip. In this state, the liquid is semiplastic and may therefore not flow out and be distributed in the strip. On the contrary, in all essentials all liquid remains in the capsule in spite of the communication way having been opened. However, as soon as the liquid becomes of low viscosity by the temperature rising above the set limit value, it diffuses out in the strip, which is capillary sucking and may have a certain property in dry state, but another property in wet state. In dry state, the strip may be non transparent or opaque, but becomes transparent when it is wet. In this connection, different prints may be made visible from a top side of the temperature indicator; all with the purpose of marking for the surroundings that the set temperature limit value has been exceeded.

Brief Description of the Appended Drawings In the drawings:

Fig 1 is a perspective view of a package for goods having a conventional bar code and a temperature indicator according to a first embodiment of the invention,

Fig 2 is an enlarged perspective exploded view showing the bar code, as well as a back side of the temperature indicator, Figs 3-5 are perspective views of the temperature indicator in three different functional states,

Fig 6 is a perspective view of an alternative embodiment of the temperature indicator,

Figs 7-9 are enlarged, schematic longitudinal sections through the first temperature indicator in the three functional states, which are shown in figs 3-5,

Fig 10 is an analogous longitudinal section through the temperature indicator according to fig 6,

Fig 11 is a diagram illustrating the melting point of an olive oil,

Fig 12 is a perspective view of a bar code and an additional alternative embodiment of a temperature indicator,

Fig 13 is an enlarged section through the temperature indicator according to fig. 12, Fig 14 is a perspective view of yet an alternative embodiment of a temperature indicator, and

Figs 15-17 are enlarged sections through the temperature indicator according to fig. 14 in three different states. Comprehensive summary of bar codes of the type EAN

Before the invention is described more in detail, it should be pointed out that bar codes of the type that are applied to packages to foods and other commodities usually consist of so called EAN codes, where the letters EAN stand for European Article Number. This constitutes a worldwide system for article numbering of all types of consumer goods. The system is administered by "International Article Numbering Association, EAN", which issues instructions for the users which are associated with the system. EAN is used in shops having computerized paydesks and a fixed or mobile bar code scanner. At the symbol scanning, a registration of the EAN code takes place in the computer system of the shop. The most common bar codes consist of price codes and weight codes, respectively. When registration takes place, a row of measures are triggered if a code is in the price memory of the computer system. The price and the merchandise description, which the shop has entered into the computer system, are shown for the customer through a price window. The specifications are printed in plain text on the. receipt of the customer and the computer adds the amount that shall be paid. At possible price changes, the goods do not need to be remarked. Furthermore, by using special programs in the computer system, there is a possibility to in an effective way assemble information, which may be combined in order to form a basis for order quantities, composition of class of goods, pricing, etc. The code scanners on the market make use of infrared light, which illuminates ■ the bars as well as the intermediate neutral fields in a barcode, the contrast between the^' bars and said fields being cru- cial for the quality of scanning. In larger scanners, the bars are illuminated by a grid of light rays. If the bars are of a dark colour, such as black or blue, at the same time as the neutral fields are light, e.g. white or yellow, an optimum contrasting effect is obtained. However, also other combina- tions of colour may exist. The essential thing is that the infrared light is either absorbed or reflected by the colours in question. Of large importance is naturally also the distinctness of the code bars. Detailed Description of Preferred Embodiments of the Invention

In fig >l _r 1 generally designates a package for goods in the form of a package for frozen or chilled goods, which in the example has a parallelepipedic, flat basic shape. In practice, the package may consist of a capsule of comparatively stiff board or cardboard. On one of the partial surfaces of the package, a bar code 2 as well as a temperature indicator according to the invention in its entirety designated 3 are applied. The bar code 2 may consist of a conven- tional price code and/or weight code (commodity code) , which may be printed on the package in connection with the same generally being provided with external printing. Alternatively, the bar code 2 may be included in a piece of tape, a label or the like, which is applied to the package afterwards. By scan- ning in an available code scanner, the bar code enables the usual data capture in a computer system of a shop.

As is seen in the exploded view in fig 2, the bar code 2 includes a plurality of code bars located between two outer bars 4 having mutually varying thickness and location. Together said code bars form an elongate, rectangular configuration. Under the code bars, there is usually also a numerical series of Arabic figures, which in the example are designated "X". In the area outside the two outer code bars, neutral fields 5, without text and pictures are left in order to enable scanning in accordance with prevalent bar code technique. In practice, said fields 5 should have a width of at least 2,7 mm in order to guarantee undisturbed code scanning. The individual code bars may have black, blue or another dark colour, while the neutral fields positioned between and out- side the code bars, may have a white, yellow or another light colour. However, the essential thing in this context is that contrasting effect is attained by the infrared light of a code scanner either being absorbed or reflected by the different colours. Reference is now made to figs 3 and 7, which illustrate the temperature indicator according to the invention in an initial state after manufacture. In the exemplified embodiment, the indicator is in the form of a label having, in applied state, an exposed, visible top side 6 and a hidden bottom side 7, which advantageously may include a finishing (not shown) by means of which the label may be pasted onto the package. In the label, two chambers 8, 9 are included the first mentioned one of which is defined by a capsule 22 and contains a fluid in the form of a liquid 10, while the second chamber 9 contains a capillary, liquid sucking means 11, which advantageously has a certain optic property in dry state, but another optic property in wet state.

In a concrete embodiment the label is assumed to be manufactured from a thin, transparent plastic foil or film 12, which is folded along an end edge 13, and welded together along two long side edges 14, 14' as well as an opposite end edge 15. Furthermore, a fourth weld 16 is made between the two chambers 8, 9, which weld in the state according to figs 3 and 7 closes the chamber 8. In the last-mentioned weld 16, one or more weakened portions 17 (see fig 4) are included which easily burst, if the liquid 10 in the chamber 8 is subjected to a certain pressure by mechanical action. In other words, the weakened material portion 17 serves as a valve between the chambers 8 and 9. Thus, when the valve is opened a communication way is formed between the two chambers 8, 9.

Fundamental for the present invention is that as fluid 10 in the first chamber 8 a liquid is chosen, which has a semiplastic consistency at temperatures below a certain limit value, but becomes liquid at temperatures above the same. For chilled goods in general and chilled foods in particular, the chosen limit value should be in the temperature range of 0 °C to +12 °C, suitably between +2 °C and +10 °C. For specific foods, the limit value may be established to either +4 °C or +8 °C.

Because the liquid in question should have the ability - depending on the ambient temperature - to transform or be converted from one viscosity state to another, more precisely between on one hand, a semiplastic - or possibly vis- cous - state and on the other hand one state of low viscosity, the liquid will henceforth be denominated conversion liquid. The choice of conversion liquid is determined by a plurality of factors, one of which consists of the character of the packaged goods. Thus, if the product consists of a food, a liquid that is not toxic and/or chemically active should be chosen. Therefore, for chilled goods, vegetable or animal oils are suitable of the type, which has a melting point or viscosity transition temperature within the range of 0-12 °C. Experiments which are the basis of the present invention have shown that olive oil is particularly appropriate. Therefore, below a brief account of a practical experiment will follow, reference being made to the chart in fig 11.

An olive oil of the make "BERTOLLI GENTILE, Extra Vergine" was cooled down in a refrigerator to a temperature of +3 °C, and then the sample was taken out in room temperature for measurement of the temperature change as well as the consistency of the oil once a minute during totally 6 min. Below the result follows of the same measurement in tabular form.

Thus, during the relatively narrow temperature range of 2,6 °C, between +6,0 °C and +8,6 °C, the olive oil in question transforms from a non liquid, semiplastic state to a state of low viscosity.

Now reference is made again to figs 3 and 7. In accordance with a preferred embodiment of the invention, the capillary means 11 being present in the chamber 9 consists of a strip of a porous or fibrous material, in par- ticular paper. Thus, experiments that are the basis of the invention have shown that paper has different optical properties in dry and wet state, respectively. More precisely, the top side or the outside of a white or brightly coloured paper is in dry state opaque so far that only the surface, but not the interior of the paper fibre web, may be seen by the eye. However, as soon as the fibre web is wet, the same becomes transparent so far that at least the outermost layer in the fibre web may be seen through. This phenomenon may according to the invention be utilized in such a way that the strip 11 is provided with one or more prints, which are invisible from the top side as long as the strip is dry, but which are made visible when the strip is wet. Although the number of prints as well as the physical shape and location thereof in the fibre web may be varied in a multiple of ways within the scope of the invention, three different prints 18, 19, 20 are shown in the example in the drawings, which all are applied on the back or bottom side of the strip 11. In this context, it should be reminded that the top side of the strip 11 is covered by the transparent plastic film 12, and is therefore always visible for the eye, while the back side of the strip is turned towards the package 1 and is therefore not exposed in the direction of the observer. The print 18 positioned closest to the chamber 8 has in the example the shape of a circular spot with the purpose of indicating that the tempera- ture indicator has been primed for use. The print 19 consists of a number of warning triangles, while the print 20, which is located in the immediate vicinity of the end edge 13, consists of a border, which extends along the major part of the width of the label. The different prints may advantageously have different colours that, however, always deviate from the colour in the strip 11. The same may advantageously be white or at least light in order to reflect infrared light of the type that is used in code scanners. The colours in the prints 18, 19, 20 should generally be darker than the white or light col- our in the strip 11. Advantageously, the colour in the print 20 may be black, while the triangular prints 19 may be yellow and/or red, and the print 18 green.

According to a preferred embodiment of the invention, the colouring substance in at least the print, which forms the border 20, may consist of a colouring substance that is soluble in the oil or the conversion liquid. In such a way, pigments from the colouring substance may be released from the print and diffuse up in the direction of the strip top side the paper, in order to additionally reinforce the visualization of the print.

The Manufacture and Function of the Temperature Indicator According to the Invention

Although series manufacturing of the label can be carried out in various ways, the print carrying strip should be pre-printed on one side thereof, and then it is contained in a double-folded plastic film, which is welded by means of the welds 15 and 16. Between said welds, two portions of the plastic film form the capsule 22, which defines the chamber 8. The same chamber is filled with conversion liquid 10. After this the strip and plastic foil are cut off, at the same time as the foil is welded at 14 and 14'. Arbitrarily long time after manufacture, the disclosed temperature indicator/the label may be primed for use, more precisely in connection with the fact that the storage period for a packaged chilled atricle should be initiated. The priming takes place by a mechanical pressure being applied against the capsule 22, which defines the chamber 8. For instance, the pressure may be provided with a finger, such as is illustrated in figs 4 and 8. When the liquid pressure is raised sufficiently high, the weakened material portion 17 in the weld 16 serving as a valve bursts, whereby the liquid 10 is free to penetrate into the second chamber 9. By executing the priming first in an environment where the ambient temperature is below the limit value, which is determined by the melting point of the liquid, it is guaranteed, however, that the liquid is not sucked into the strip 11 in its entirety. The still semiplastic liquid will accordingly only penetrate a short distance in one end portion of the strip, such as is shown at 21 in fig 8. Hereby, the liquid wets the print 18, whereby it is visually indicated that the indicator has been primed. In practice, the capsule 22 is punctured earliest in connection with the indicator being applied to the package 1 and/or the goods being inserted in a refrigerating space, for instance at a manufacturer/distributor or in a shop. In this state according to fig 8, the strip 11 is unaffected by the liquid with the exception of the end portion 21. In other words, the prints 19 and 20 are still hidden under the surface layer turned outwards of the paper fibre web.

Suppose that the temperature limit value in question for the goods is set to +8 °C. As long as the ambient tempera- ture is below the same value, the label remains in the state that is shown in fig 8. If however, the temperature during keeping of the goods would exceed +8 °C, the consistency of the liquid will be converted from semiplastic to of low viscosity. By means of capillary effect in the porous strip 11, the liquid will then be sucked into the strip and completely wet the same, such as is illustrated in fig 9. In doing so, the two prints 19 and 20 will appear and become visible from the outside of the label. In this way, the observer is made aware that the temperature limit value has been exceeded. In accordance with a preferred embodiment of the invention, the described label is applied in the immediate vicinity of the bar code 2 of the package 1. More precisely, the label is placed having the end edge 13 thereof in the immediate vicinity of an outer code bar 4. In practice, the dark, borderlike print 20 in the label should be located at a distance within the range of 0,2-2,0 mm from the outer code bars 4 of the bar code. In such a way, it is guaranteed that conventional code scanning without hindrance can be carried out as long as the strip 11 is dry and white/light, but as soon as the strip is wet the dark border 20 appears and makes scanning of the code impossible because the border absorbs the infrared light of the code scanner.

Within the scope of the invention, it is possible to in the second chamber 9 provide means in order to in one or more points delay or counteract the penetration of the liquid fluid in the direction of the end edge 13. In fig 10, an example is shown of such a means in the form of a constriction 23 where the paper strip or the fibre web 11 is compressed so that penetration of the liquid is made more difficult. The same effect may also be attained by making the fibre web with spaced apart sections, which have different porosity or capillary effect. By in this way delaying the liquid penetration, it is guaranteed that the article has to be exposed to a harmfully increased temperature during a certain time so that the indicator will be triggered. A short exceeding of the temperature limit value, e.g. during the time which the customer stays in a shop (usually max. approx. 30 min), will therefore not lead to the indicator being triggered. Delay of the penetration of the liquid in the strip may also be aided by supplying an additive to the oil or the conversion liquid, which thickens the liquid so that the same gets a higher viscosity, i.e., becomes more viscous than in the original state thereof, after having passed the tempera- ture limit value.

The embodiment shown in fig 6 differs from the embodiment according to figs 3-5 in such a way that the print 19 is formed with two fields 19', 19", which have different colours. For instance, the field 19' may be yellow and the field 19" red. As the conversion liquid penetrates into the fibre web the eye may - thanks to the different colours - easily observe a progressive unfreshness of the goods.

In this connection it should also be mentioned that as print in the strip, a number of code bars may be included, which may form a complement to the ordinary bar code 2 of the package in order to upon the data capture in connection with the code scanning indicate that the temperature limit value has been exceeded. Thus, in this case, the code scanning is not made impossible, but upon the scanning the computer system will receive information about a limit value exceeding having occurred. Such code bars may also be applied to the casing of the indicator.

Reference is now made to figs. 12 and 13 that illustrate a third, alternative embodiment of the temperature indi- cator. In this case, conversion liquids 10 are contained in two separate capsules 22, which are integrated in the strip 11. The integration of the capsules in the strip may be realized in various ways, e.g. by locating the capsules inside the fibre mass, or by housing the capsules in recesses in the strip. The only essential is that the capsules are contained in the cover that is formed by the film 12, which advantageously is in close contact with the outside of the strip. In figs 14-17, an additional embodiment is shown according to which the oil or the conversion liquid is not contained in any capsule of its own. In this case, the strip 11 may be formed with a recess 24, which is accessible via an opening 25 in the film cover 12 that contains the strip 11. In the recess 24 may be applied via the opening 25 one or more drips of a conversion liquid, which has a temperature below the limit value in question. In other words, the individual drip may be supplied in the semiplastic state thereof so that it cannot flow out in the fibre mass of the strip. After application of the liquid in the recess, the last-mentioned one is sealed by means of a covering film 26 (see fig 16) . In fig 17, the temperature indicator is shown in a triggered state after an exceeding of the set temperature limit value. In this state, the initially semiplastic liquid has become liquid and been able to diffuse out in the strip while making the prints 19, 20 visible.

It is even feasible to spare the abovementioned recess and supply the conversion liquid in a liquid state via the opening 25 in the cover 12. However, this requires that the temperature indicator, after supply of the liquid together- with sealing of the supply opening, is cooled down fast to a temperature below the limit value in question. In such .a way it is guaranteed that the initially liquid fluid is brought to a semiplastic state fast, in which it cannot diffuse out in the porous means .

Advantages of the Invention

An advantage of the temperature indicator according to the invention is that the same is mechanically stable and can be manufactured in a simple and cost-effective way, above all as a consequence of the same including only one active fluid or liquid as well as a passive, capillary sucking means, e.g. in the form of a paper strip. In other words, the indicator does not require any mixing of different liquids in order to be activated for the freshness monitoring function thereof. By choosing a non toxic conversion liquid, such as a vegetable oil, also the risk of contamination of sensible goods, such as foods, is obviated. A further advantage is that the indicator may be made entirely temperature independent as long as the same has not been primed by puncture of a capsule, which contains the conversion liquid. After manufacture, such an indicator may accordingly be kept and transported during arbitrary temperature states - also at temperatures below 0 °C - without the capability to function of the liquid being lost. Not until after the priming, which takes place at a temperature below the set limit value, is the temperature and freshness monitoring function of the liquid activated. Furthermore, the indicator has a stable transparency upon recooling. If the temperature limit value has been exceeded and the strip or the capillary means becomes transparent by wetting, said transparency remains even if the goods together with the indicator again are chilled or frozen to a temperature below the limit value. Furthermore, the mechanical and capillary sucking properties of the indicator may simply be altered, and good repeatability of the parameters temperature/time being obtained.

Feasible Modifications of the Invention

The invention is not limited to the embodiments described above and shown in the drawings. Thus, it is feasible to use, instead of a paper strip, other liquid sucking means. For instance, powder or fibrous coatings may be used on the inside of the outer plastic film (or a combination of this) . Significant is only that the used means has different optical properties in dry and wet state, respectively. Furthermore, it is feasible to add to the used conversion liquid, e.g. oil, one or more viscosity regulating means, for instance with the purpose of guaranteeing a distinct transition from semiplastic to liquid consistency at a desired temperature limit value. Although the invention above has been described primarily in connection with chilled goods, i.e., goods which are kept in the temperature range 0-12 °C, the general idea according to the invention is also applicable to frozen foods, i.e., goods which are kept at temperatures below 0 °C. In other words, a conversion liquid may be used the melting point of which is below 0 °C, e.g. in the interval of 0 °C to -20 °C. It should also be mentioned that other liquids than oil may be utilized as conversion liquid. As examples of liquids having melting points near 0 °C should be mentioned ani- line (-6 °C) , formic acid (+8 °C) , dichloroacetic acid (+11 °C) , formamide (+2,6 °C) and glycerol (+18 °C) ^'. Also ten- sides may form or be included in the conversion liquid. To the liquid in question may be added different additives, such as alcohol, salts, etc, in order to fine adjust the desired temperature limit value. It should also be pointed out that the indicator not necessarily has to be realized in the form of a separate label. Thus, it is feasible to integrate the indicator with the proper package already in connection with the production of the same. Furthermore, the indicator may include other visualization means than prints on or in a strip or other capillary means. Thus, it is feasible already in the proper conversion liquid or the strip/the capillary means to insert colouring agent, e.g. pigments, which in one way or the other colours the capillary means when the liquid flows out in the same.

Although EAN codes are the most common form of commodity codes, in particular for foods, the invention is also applicable in connection with other types of commodity codes, which makes use of bars or barlike symbols. Examples of such codes are Interleaved 2/5, Code 39, Code 128, as well as PDF- 417. Characteristic also of these codes is that the bars or the symbols form a rectangular configuration in the extension of which a temperature indicator according to the invention can be applied.

Claims

1. A temperature indicator for packages (1) intended for keeping goods in a preservative state in which the temperature must not exceed a certain limit value, comprising a porous, capillary sucking means (11), as well as at least one liquid (10), by means of which the porous means is wettable with the purpose of triggering a visualization of the ambient temperature having exceeded the limit value, characterized in that said liquid (10) consists of a liquid, which has semiplastic consistency at temperatures below said limit value, but becomes liquid at temperatures above the same in order to flow out in the porous means .

2. A temperature indicator according to claim 1, characterized in that the liquid (10) at least partly consists of an oil.

3. A temperature indicator according to claim 1 or 2, characterized in that the capillary sucking means consists of a strip (11), in which at least one print (18, 19, 20) is included, which is invisible from a top side of the strip as long as the strip is dry but which is made visible when the strip becomes transparent by wetting.

4. A temperature indicator according to claim 3, characterized in that the print (18, 19, 20) is provided by means of a colour, which is soluble in said liquid (10) .

5. A temperature indicator according to any one of the preceding claims, characterized in that at least a certain part of the capillary sucking means (11) in a dry state has a light or light reflecting colour, but gets a partially dark or light-absorbing colour when the strip is wet.

6. A temperature indicator according to any one of the preceding claims, characterized in that the same includes means (23) in order to delay or counteract the penetration of the liquid (10) into the capillary sucking means (11) .

7. A temperature indicator according to claim 6, characterized in that the delay means consists of one or more constrictions (23) in which the capillary sucking means (11) is compressed.

8. A temperature indicator according to claim 6, characterized in that the delay means comprises an additive added to the liquid (10) and having the purpose of thickening the liquid in the liquid state thereof.

9. A temperature indicator according to any one of claims 4-8, characterized in that a plurality of different prints (18, 19, 20) having different information messages and/or specifications are arranged along the length extension of the strip (11) .

10. A temperature indicator according to any one of the preceding claims, characterized in that the liquid (10) is contained in an openable capsule (22) .

11. A temperature indicator according to any one of claims 1- 9, characterized in that the liquid (10) is introduced in a cover (12) containing the porous means (11) via an opening (25) in the same cover and is in direct contact with the porous means .

12. A temperature indicator according to any one of claims 4-

11, characterized in that a number of code bars are included in the same and intended to form or be included in a bar code.

13. A package for keeping goods in a preservative state in which the temperature must not exceed a certain limit value, characterized in that the same comprises a temperature indicator (3) according to any one of claims 1-12.

14. A package according to claim 13, comprising also a bar code (2) of the type that between two outer, light absorbing code bars (4) includes a plurality of intermediate, likewise light absorbing code bars mutually spaced-apart by neutral, light reflecting fields, outside the outer code bars outer neutral fields (5) being present, characterized in that the temperature indicator (3) is located beside the bar code (2) in close connection with one of the outer code bars (4) thereof without covering the bar code, in order to, on one hand, at a first temperature below the limit value without hindrance enabling scanning of the bar code, but, on the other hand, after triggering of the temperature indicator by exceeding of the temperature limit value either make scanning impossible by making an outer, neutral field (5) light absorbing or supplementing the bar code by the fact that code bars included in the temperature indicator are brought to appear.

15. A method of monitoring the freshness of goods kept in packages, more precisely by means of temperature indicators included in the packages, characterized in that as temperature indicator a temperature indicator (3) according to any one of claims 1-12 is used.