GB2318871A - Temperature change indicating device - Google Patents

Abstract

A temperature change indicating device is inactive before priming, is primed by subjecting it to a first temperature less than or equal to a pre-determined first temperature, at which successful priming is visually apparent, and undergoes a permanent visible change when subjected to a second temperature greater than or equal to a pre-determined second temperature. The device comprises two chambers (1,5), the chamber (1) containing water and citric acid (2) and constructed of flexible polymer provided with a weak point (3) so that on freezing the weak point (3) is ruptured by expansion to prime the device. When the ambient temperature rises to 0{C, the water-citric acid (2) melts and contacts the indicator (4) (eg litmus paper) and changes its colour. The chamber (5) is rigid or flexible, and transparent. The weak point may be wax, or be brittle when primed. The device is attached to a food product or storage place.

Description

TEMPERATURE CHANGE INDICATOR The present invention relates to a temperature change indicator, a method for the manufacture and for the priming thereof and applications thereof, more particularly to a tamper proof device adapted to undergo a permanent visible change as a result of undergoing an undesired temperature change, methods for the manufacture and priming thereof and applications thereof, most particularly to such devices for commercial or domestic use as indicator of such temperature change of an object or locus with which it is associated.

Within the food and pharmaceutical industries it is common practice to transport, store and supply products below specified storage temperatures for preservation thereof for a specified "best by" and "consume by" period. It is in particular critical that a food product or part thereof does not rise above a specified maximum temperature, even if thereafter restored to the specified storage temperature, since this results in bacterial contamination of the product which may cause discomfort or sickness on consumption thereof. Changes in texture may also lead to unacceptable quality loss. The effect of such temperature change in pharmaceutical products can lead to loss of effect or undesired side effects on administration to a patient.

Disclosures of temperature change indicators which provide an indication of such undesired transition relate to visual indicators which are activated if the storage temperature of a product has been exceeded at any point in the product's storage cycle. Such devices are of permanent or transient nature, the former being termed a "one-shot device", and are electronically, mechanically or chemically based.

Electronic sensors and mechanical type one shot indicators are presently too expensive for inclusion in individual frozen food products and read-out requires high technology sensors and displays, rendering their extensive application impractical and commercially unattractive. Chemical devices have been disclosed, for example employing one or more different coloured liquids frozen to form individual coloured crystals within a container, which melt and mix when subject to an undesired temperature change, taking on a different recognisable colour or colour combination. However most thermochromic pigments are transient in operation and revert to their original colour on recooling, and are thereby ineffective in indicating a single transgression of the specified maximum temperature. Complex organo-metallic compounds do exhibit a temperature change in the critical range, but are characterised by substantial temperature hysteresis, whereby they retain the indicator temperature colour on reverting to the desired temperature and therefore may be regarded as semi permanent. However it will be apparent that the original temperature colour may be regained by deliberate depression to substantially reduced temperatures, whereby these devices are not tamper proof.

Accordingly there is a need for a simple, reliable and inexpensive device which is adapted to undergo a permanent visible change as indication of elevation beyond a maximum desired temperature of a product or locus with which it is associated. Such device must be tamper proof and critically sensitive to provide customer confidence and protection at point of sale and thereafter.

We have now surprisingly found that a device may be provided which meets the above needs in admirable manner, is characteristically tamper proof, reliable and is adapted for convenient manufacture.

In its broadest aspect there is provided according to the present invention a temperature change indicating device which is adapted to be primed by subjecting to a first temperature less than or equal to a pre-determined maximum temperature, at which successful priming is visually apparent, and which is adapted to undergo a permanent visible change when subjected to a second temperature greater than or equal to a pre-determined minimum temperature, which is constructed in manner whereby the temperature change indication mechanism is substantially inactive prior to priming thereof.

It is a particular advantage that the device of the invention is adapted for quality control at the priming stage thereof prior to being commissioned for use, moreover may be provided in manner that tampering is possible only by means of discarding and replacing with a new device, whereby tampering may be evident from damage to the product or locus with which it is associated. A product or locus may comprise any food, health, pharmaceutical or like product or a freezer compartment for transport, storage of the like, whether for domestic or commercial use.

Preferably the device comprises at least two chambers having at least one common wall, partition or part thereof in which is provided one or more identifiable weak points, the first chamber being adapted to contain fluid and the second chamber being adapted to contain an indicator medium which is adapted to undergo a permanent visible change on contact with the fluid, wherein the device is adapted to be primed by subjecting to a first temperature as defined below that at which the fluid freezes or solidifies and simultaneously expands causing rupture of the weak point, and to be activated by subjecting to a second temperature as defined at which the frozen or solidified fluid reverts to fluid form in contact with the indicator medium.

Reference herein to an identifiable weak point is to a design flaw, weak seal or otherwise rupturable means separating the two chambers which is adapted to rupture in hereinbefore defined manner on priming. Such weak point must be sufficiently reliable or controllable to ensure rupture when subject to a predetermined pressure which is a function of the volume of the first chamber and fluid respectively and of the expansion pressure of the fluid on solidifying or freezing. It is a particular advantage that the failure of the weak point, i.e.

whereby it fails to rupture on priming, is visibly apparent, whereby a device may be discarded prior to association with a product or locus for temperature change indication purpose. This ensures reliable quality control and moreover dispenses with the need for complex or intricate mechanisms or manufacture directed to providing a 100% reliable device. Nevertheless it will be apparent that the nature of the priming mechanism is such as to provide a desired degree of reliability by selection of appropriate weak point design.

It will be appreciated that the common wall or part thereof serves to maintain the fluid and indicator medium out of contact prior to priming thereof, whereby premature activation is substantially prevented. Moreover the second chamber wall is provided substantially for purpose of ensuring contact of fluid and indicator on activation thereof and preventing leakage of fluid or indicator causing contamination of a product or locus and preventing premature activation of the device by contact with other materials in the vicinity of the product or locus to which it is adapted to be associated.

The chambers may be constructed of any desired material suited for the above purpose. Preferably the second chamber or part thereof is constructed of transparent material enabling conveniently visible inspection of the indication means. Preferably the first and/or second chamber, or part thereof, which is adapted to be associated with, and preferably intimately contacted with a product or locus for temperature change indication purpose, is constructed of material enabling rapid and efficient thermal contact, by virtue of the thermal conductivity of the material itself or by a wall thickness which is insufficient to hinder thermal contact.

The first or second chamber walls, or part thereof, which are adapted to be positioned remote from a product or locus for temperature change indication purpose may conveniently be constructed of material providing poor thermal contact, in contrast to that of the chamber walls, or part thereof, which are proximal with such product or locus, whereby the indicator is relatively insensitive to atmospheric temperatures and is particularly sensitive to temperature of product or locus. This is of particular importance for use in temperature change indication of products or locuses having a lesser bulk heat capacity than the fluid of the device, whereby resistance to temperature change would be significantly lower in the device of the invention than in the surface of the product or locus itself.

The chambers may for example be comprised of substantially flexible, nontoxic, conveniently shaped or formed material having the hereinbefore defined properties, and which may be characterised by a high solvent resistance and a mechanical integrity sufficient for damage resistance on handling and the like.

Preferably the chamber walls are constructed of one or more flexible or rigid polymers which may be self-sealing, for example is capable of bonding to itself, or may be readily sealed by the application of heat or of a sealant Alternatively the chamber walls may be constructed of a substantially resilient material which may be sealed by locating a suitable formable or resilient material in an aperture thereof in manner to provide an effective closure. For example formable or resilient material may comprise wax or other non-permeable material such as plastics material located to provide a plug closure of the chamber.

In a particular embodiment of the invention, the first chamber or its closure may be comprised of a material as hereinbefore defined which is adapted to provide a weak point as hereinbefore defined as a result of priming the device, and which moreover is inelastic or becomes inelastic on priming the device. For example the material may undergo a ductile or plastic to brittle transition when subject to a first temperature as hereinbefore defined. This has the advantage that the pressure required to rupture the weak point(s) as hereinbefore defined may be less than that which would be required with a plastic first chamber, and particularly advantageously, that the first chamber wall is adapted to generate flaw(s) or weak point(s) as hereinbefore defined, i.e. to fracture or crack, as a result of pressure applied and temperature induced transition to brittle form.

Preferably such material is selected from any suitable natural or synthetic wax or polymer having temperature dependent properties as hereinbefore defined, and adapted in known manner to provide the required temperature sensitivity, for example by selection of wax source determining the cohesion properties thereof, or of polymer by number average molecular weight, nature and type of linking groups, combination with other components such as comonomers or chain-terminating agents and the like.

The device, and the chambers thereof may be of any desired shape or form, and may be provided in manner that the first chamber is adjacent and external to the second chamber, having a weak point therebetween, or (partially) enclosed by the second chamber having a weak point enclosed by the second chamber.

Preferably the device and chambers thereof are of suitable shape or form adapted for convenient association with a desired product or locus, and for effective contacting of fluid and indicator medium on activation. Preferably the device and containers are of cylindrical, elongate, disc or like form whereby they are adapted to be substantially continuous with the surface of a geometrical or irregular shaped product or locus, thereby minimising the risk of mechanical damage or dissociation.

First and second chambers may be independently rigid or non-rigid or a combination thereof. Preferably at least one of the first and second chambers is rigid, thereby providing protection from impact damage or the like.

The fluid may be any liquid or gas, preferably comprises a liquid which expands on freezing, for example water or aqueous solutions. It will be apparent that water is ideally adapted to the present application by virtue of the characteristic expansion thereof on freezing, the ability to flow in fluid form under the action of gravity and capillary forces, and the use with suitable additive for a number of indicator mediums in which a colour change is brought about on mutual contact thereof.

Accordingly it will be apparent that a device of the invention may be provided for purpose of indicating a temperature transition in the region of 0 C, for example wherein the first temperature is less than OOC and the second temperature is greater than or equal to OOC. The fluid may comprise an aqueous solution including freezing point depressants, elevators and the like whereby the transition temperature for indication may lie in the range of -20 C to +5"C.

Such freezing point modifying agents are known in the art, for example soluble salts such as sodium chloride and the like.

The indicator may be selected to undergo any desired visible change as hereinbefore defined, and is preferably selected to undergo a distinctive colour change. The indicator may comprise a preferably non toxic medium which undergoes a change in pH, oxidation state, hydration change or the like on contact with aqueous solutions of acids or bases, oxidation or reducing agents, other chemicals and the like. Any acid base indicator may be employed which can exist as either protonated or unprotonated form and of which one form is coloured, whereby the non-toxic fluid additive may comprise citric acid, and like edible acidic or alkaline food additive. Preferably the indicator comprises litmus wherein the first temperature colour is characteristically blue and the second temperature colour is characteristically red, or methyl orange for which the first temperature colour is characteristically transparent and the second temperature colour is characteristically orange. Alternatively an indicator may comprise a salt or compound which may exist in two oxidation states, one of which is coloured, and which may be converted from a first to second oxidation state by the addition of an oxidising or reducing agent, which change is permanent. For this purpose salts of iron or like edible salt may be employed.

Printing of indicator medium in limited regions may permit a written warning to become visible on colour change.

Suitably the amount of indicator medium and/or fluid additive and concentrations thereof is selected to ensure a detectable colour change.

Optionally the second chamber wall, or part thereof, which is adapted to be associated or intimately contacted with a product or locus as hereinbefore defined is non-transparent, at least for a portion serving as a background to the indicating means, whereby the indicator medium colour is easily visible, regardless of the colour of the product or locus itself.

The indicator medium may be provided in desired form within the second chamber, whereby reliable contact with fluid on activation of the device is ensured. Conveniently, the indicator medium is supported in convenient manner, for example is impregnated onto paper, or like continuous integral deformable material, which is adapted to be located in contact with or associated with the common wall.

Such impregnated material for example may conveniently be wrapped around the first chamber, where this is contained within the second chamber. The manner of wrapping the material may be selected such that the material is supported by the first or second chamber wall or part thereof, and in direct contact therewith or otherwise. For example impregnated material may be of substantially similar shape of profile to the first and/or second chamber wall or part thereof, and located therebetween, optionally at a predetermined distance from either or both, or comprised integrally with either.

It is a particular advantage of the invention that the shape and form of such indicator material may allow for accurate positioning thereof within the device, for example with respect to a weak point at which rupture takes place, whereby contact of fluid and indicator medium is assured to a sufficient degree to be detectable as hereinbefore defined.

Optionally the indicator medium comprises a semi-permeable membrane at the face thereof which prevents contact with the frozen or solid fluid on priming of the device, but allows contact due to gravitational or capillary action of liquid fluid.

The device may be comprised as one of a plurality thereof whereby a historical record may be kept for a product or locus. For example such multiple device may serve to ensure temperature is not transgressed at certain critical points in the life of a product or locus, for example prior to and following a sale of a food product respectively, at each of a regulated periodic inspection of a freezing compartment for domestic or commercial use and the like. Such multiple device may be conveniently provided in the form of tear off strips whereby removal of a strip is apparent and association with a product or locus is convenient and simple.

The device may comprise any suitable means for association with or attachment to a product or locus. Such attachment means may comprise a mounting adapted for convenient insertion and removal or may comprise a suitable integral attachment means whereby removal leads to visible distortion, marking or other damage of the product or locus. The latter is of particular advantage where it is desired to provide a tamper proof device. For example the device may be heat sealed to the surface of a product or locus, or may be provided within the packaging thereof and adjacent a visible portion thereof for visible inspection purpose.

In a further aspect of the invention there is provided a method for the manufacture of a device as hereinbefore defined.

In its broadest aspect therefore there is provided a method for the manufacture of a device as hereinbefore defined comprising providing a temperature change indicating device which is adapted to be primed by subjecting to a first temperature less than or equal to a pre-determined maximum temperature, at which successful priming is visually apparent, and which is adapted to undergo a permanent visible change when subjected to a second temperature greater than or equal to a pre-determined minimum temperature, which is constructed in manner whereby the temperature change indication mechanism is substantially inactive prior to priming thereof.

Preferably a method for manufacture of a device as hereinbefore defined comprises encapsulating fluid as hereinbefore defined in a first chamber, providing indicator means as hereinbefore defined in contact with or associated with an exterior wall of the first chamber and encapsulated in a second chamber, wherein the first chamber is provided with or sealed in manner to provide, one or more identifiable weak points in a common wall between the first and second chambers.

The first chamber may be provided in any suitable manner, for example an open pre-formed chamber may be filled with fluid and sealed, whereby the chamber may be pre-formed to include an identifiable weak point or the sealing point may form a such weak point. Preferably the pre-formed chamber comprises the identifiable weak point for purposes of reliable rupture. Preferably the chamber is substantially completely filled with fluid, whereby rupture thereof on priming is assured.

The sealed first chamber may be associated with the indicator means and the whole thereof encapsulated in a pre-formed or simultaneously formed second chamber for subsequent sealing. Suitably means are provided to ensure that fluid which may have become associated with the outside of the first chamber during filling or sealing thereof is removed, for example by means of rinsing the first chamber with an inert medium. Alternatively the indicator means is provided in manner that a second encapsulation or additional semi-permeable membrane wall is provided associated with the first chamber and separating it from the indicator means. Such membrane would be sufficient to prevent contact with the indicator means by gravitational or capillary forces of minute excesses of fluid, however would not be sufficient to prevent contact with the body of fluid in its fluid form, i.e. on activation thereof.

In a further aspect of the invention there is provided a method for the priming of a device as hereinbefore defined comprising bringing the device to a first temperature as hereinbefore defined whereby the fluid freezes or solidifies, and associating the product with a product or locus for temperature change indication purpose, prior to, simultaneously with or directly after priming thereof.

Preferably the device is associated with a product or locus as defined subsequent to priming thereof, whereby effective quality control may be performed and faulty devices discarded without the need for removal from a product or device, where tamper proof association is to be employed. Preferably the device is associated with a product or locus prior to or simultaneous with priming thereof, for convenience of handling and attachment, where removable association is envisaged.

In a further aspect of the invention there is provided a method for the attachment of a device as hereinbefore defined to a product or locus as hereinbefore defined for temperature change indication purpose.

In a first embodiment attachment may be by tamper proof means whereby removal or replacement of the device is readily apparent by inspection of the product or locus. For example a device may be associated with a product or locus during the packaging thereof, whereby it may be removed only by removal of the packaging. Suitably such means requires that the packaging, or a part thereof, is transparent. It will be apparent that heat transfer ability between such product or locus and a device of the invention is therefore facilitated, without need for attention to the nature of the product or locus packaging. Alternatively a product or locus may comprise a suitable recess in which a device may be located and secured. For example the product or locus packaging may comprise integral external extensions adapted to be formed into the second chamber about a first chamber located at the surface or in a suitable recess of the surface of a product or locus as hereinbefore defined, whereby removal causes damage to the product or locus packaging. Alternatively the product or locus may comprise physical attachment means into which a device as hereinbefore defined may be inserted in tamper proof manner, i.e. employing suitable non-returning flanges, concealed springs and the like which advance on insertion of the device and can be retrieved for removal thereof only by destruction of the attachment means.

In an alternative embodiment attachment may be by convenient insertion means enabling removal of the device at will.

Preferably the attachment means is robust, whereby it remains intact despite a degree of rough handling, prolonged storage at a temperature as hereinbefore defined and the like.

In a further aspect of the invention there is provided a fluid or an indicator means as hereinbefore defined for use in the manufacture of a device as hereinbefore defined. Suitably fluid and indicator means are prepared as component parts in the requisite concentration, quantity, volume or the like.

In a further aspect of the invention there is provided the use of a device as hereinbefore defined for temperature change indication of a product or locus as hereinbefore defined. Such use may be for commercial or domestic use as defined.

In a further aspect of the invention there is provided a product or locus as hereinbefore defined comprising a device as hereinbefore defined in primed or un-primed form.

The invention is now illustrated in non-limiting manner with reference to Figures 1 to 7 which are plan and end views of devices as hereinbefore defined.

In Figure 1 is shown a chamber (1) constructed of a flexible polymer as hereinbefore defined and containing a solution (2) of substantially pure water with citric acid. The chamber (1) comprises an identifiable weak point (3) which is formed by thermally sealing the chamber (1) during the manufacture thereof. The weak point (3) is adapted to rupture on freezing expansion of the contents (2). Indicating means (4) is provided and supported on a paper which is conveniently formed into a closed loop for placing around chamber (1). A second chamber (5) is provided encapsulating the whole as indicated, and comprising a transparent flexible material, suitably a polymer, to ensure correct functioning of the device and prevent environmental contamination.

In Figures 2 to 7 are shown alternative devices comprising substantially cylindrical first chamber (1) constructed of plastic tubing and containing solution (2) of substantially pure water with citric acid as hereinbefore described for Figure 1. In each case the chamber (1) comprises an identifiable weak point (3) which is formed in a wax plug (6) sealing chamber (1) within second chamber (5). The weak point (3) is adapted to rupture as hereinbefore defined.

In Figure 3 which represents the end view of the device of Figure 2 is shown indicating material comprising blue litmus paper (4) supported on the internal wall of second chamber (5), suitably positioned with respect to the first chamber (1). The second chamber (5) comprises a rigid plastic cover which serves to protect the device as a whole from impact damage and the like.

In Figures 4 to 6 which represent alternative devices are shown different forms of the first chamber (1) comprising cap or plug (6) of a similar cross-sectional area to the chamber itself, or of lesser cross-sectional area and located in a constriction (8) at one end of the cylindrical chamber. In each case the indicating material comprising a disc of indicator paper (4) is located with respect to the cap or plug (6) and substantially in a plane parallel to the cap or plug (6) or the end of the chamber associated therewith. In each case the second chamber (5) may be rigid or flexible and is at least partially transparent. A flexible chamber (5) comprises a close wrap about a rigid first chamber (1) thereby holding the indicator paper in position.

In Figure 7 which represents the end view of the device of Figure 6 is shown the nature of the second chamber (5) which comprises a rigid cylindrical chamber having a transparent end cover (7) in which is seated the indicator (4) having a disc shaped recess adapted to receive the cap (6) located in the constriction (8) of first chamber (1).

The devices of the Figures are adapted to be primed by freezing thereof, whereby weak point (3) ruptures when the pressure of freezing fluid (2) becomes excessive. Suitably the weak point is adapted to rupture at an advanced stage of freezing, whereby unfrozen fluid (2) is not released into chamber (5). So long as the device is maintained below the freezing point of fluid (2) it may not be activated. However on raising to a pre-determined temperature in the region of 0 C, the frozen fluid (2) melts whereby it becomes subject to gravitational and capillary forces and comes into contact with indicator means (4), whereby the indicator, such as litmus reacts to the change in pH and undergoes colour change. The colour change is permanent and irreversible, even on re-freezing of the device.

Further advantages of the invention will be apparent from the foregoing.

Claims (24)

1. Temperature change indicating device which is adapted to be primed by subjecting to a first temperature less than or equal to a pre-determined maximum temperature, at which successful priming is visually apparent, and which is adapted to undergo a permanent visible change when subjected to a second temperature greater than or equal to a pre-determined minimum temperature, which is constructed in manner whereby the temperature change indication mechanism is substantially inactive prior to priming thereof.

2. Temperature change indicating device as claimed in Claim 1 which comprises at least two chambers having at least one common wall, partition or part thereof in which is provided one or more identifiable weak points, the first chamber being adapted to contain fluid and the second chamber being adapted to contain an indicator medium which is adapted to undergo a permanent visible change on contact with the fluid, wherein the device is adapted to be primed by subjecting to a first temperature as defined in Claim 1, below that at which the fluid freezes or solidifies and simultaneously expands causing rupture of the weak point, and to be activated by subjecting to a second temperature as defined in Claim 1, at which the frozen or solidified fluid reverts to fluid form in contact with the indicator medium.

3. Temperature change indicating device as claimed in Claim 2 wherein an identifiable weak point is a design flaw, weak seal or otherwise rupturable means separating the two chambers which is adapted to rupture on priming when subjected to a predetermined pressure which is a function of the volume of the first chamber and fluid respectively and of the expansion pressure of the fluid on solidifying or freezing.

4. Temperature change indicating device as claimed in any one of Claims 1 to 3 wherein the second chamber or part thereof is constructed of transparent material enabling conveniently visible inspection of the indication means.

5. Temperature change indicating device as claimed in any one of Claims 1 to 4 wherein the first and/or second chamber, or part thereof, which is adapted to be associated with, and preferably intimately contacted with a product or locus for temperature change indication purpose, is constructed of material enabling rapid and efficient thermal contact.

6. Temperature change indicating device as claimed in any one of Claims 2 to 5 wherein the chambers are comprised of substantially flexible, non toxic, conveniently shaped or formed material characterised by a high solvent resistance and mechanical integrity.

7. Temperature change indicating device as claimed in Claim 6 wherein the chamber walls are constructed of one or more polymers, optionally self-sealing, or readily sealed by the application of heat or of a sealant or of a substantially resilient material which may be sealed by locating a suitable formable or resilient material in an aperture thereof in manner to provide an effective closure.

8. Temperature change indicating device as claimed in any one of Claims 1 to 7 wherein the first chamber or its closure is constructed of a material adapted to provide a weak point as a result of priming the device, which material is inelastic or becomes inelastic on priming the device.

9. Temperature change indicating device as claimed in any one of Claims 1 to 8 wherein the first chamber is adjacent and external to or (partially) enclosed by the second chamber.

10. Temperature change indicating device as claimed in any one of Claims 2 to 9 wherein the fluid comprises a liquid which expands on freezing, particularly water or aqueous solution, optionally including freezing point depressants, elevators and the like.

11. Temperature change indicating device as claimed in any one of Claims 1 to 10 wherein permanent visible change comprises a distinctive colour change provided by a non toxic indicator medium which undergoes a change in pH, oxidation state, hydration change or the like on contact with aqueous solution of acid or base, oxidation or reducing agent, other chemicals and the like.

12. Temperature change indicating device as claimed in Claim 11 wherein the second chamber wall, or part thereof, is non transparent, at least for a portion serving as a background to the indicating means, against which the indicator medium colour change is visible.

13. Temperature change indicating device as claimed in Claims 11 or 12 wherein the indicator medium is impregnated onto paper or a like continuous integral deformable material, which is adapted to be located in contact with or associated with the common wall.

14. Temperature change indicating device as claimed in any one of Claims 11 to 13 wherein the indicator medium is printed in limited regions permitting a written warning to become visible on colour change.

15. Temperature change indicating device as claimed in any one of Claims 11 to 14 wherein the indicator medium comprises a semi-permeable membrane at the face thereof which prevents contact with frozen or solid fluid on priming of the device, but allows contact due to gravitational or capillary action of liquid fluid.

16. Temperature change indicating device as claimed in any one of Claims 1 to 15 which is adapted to be associated with a product or locus for temperature change indication purpose, particularly a food, health, pharmaceutical or like product or a freezer compartment for transport, storage, domestic or commercial use.

17. Temperature change indicating device as claimed in any one of Claims 1 to 16 which comprises means for association with or attachment to a product or locus.

18. Method for the manufacture for a device as claimed in any one of Claims 1 to 17 comprising providing the temperature change indicating device which is adapted to be primed by subjecting to a first temperature less than or equal to a pre-determined maximum temperature, at which successful priming is visually apparent, and which is adapted to undergo a permanent visible change when subjected to a second temperature greater than or equal to a pre-determined minimum temperature, wherein the device is constructed in manner whereby the temperature change indication mechanism is substantially inactive prior to priming thereof.

19. Method as claimed in Claim 18 for the manufacture of a device as claimed in any one of Claims 2 to 17 which comprises encapsulating fluid in a first chamber, providing indicator means in contact with or associated with an exterior wall of the first chamber and encapsulated in a second chamber, wherein the first chamber is provided with or sealed in manner to provide, one or more identifiable weak points in a common wall between the first and second chambers.

20. Method for the priming of a device as claimed in any one of Claims 2 to 17 which comprises bringing the device to a first temperature whereby the fluid freezes or solidifies, and associating the product with a product or locus for temperature change indication purpose, prior to, simultaneously with or directly after priming thereof.

21. Method for the attachment of a device as claimed in any of Claims 1 to 17 to a product or locus as defined for temperature change indication purpose.

22. Method as claimed in Claim 21 wherein attachment is by tamper proof means whereby removal or replacement of the device is readily apparent by inspection of the product or locus.

23. Fluid or indicator means as defined for use in the manufacture of a device as claimed in any one of Claims 2 to 17.

24. Product or locus according to Claim 16 comprising a device as claimed in any one of Claims 1 to 17 in primed or unprimed form.