GB2461865A - A Device to Indicate the Occurrence of a Defrost Event - Google Patents

Abstract

A safety device 10 can indicate the occurrence of defrosting events within a freezer or freezer compartment. The device has a housing containing a freezable medium 16 which is able to change between a first frozen state and a second unfrozen state in response to a defrosting event. The device also includes an indicator 18 disposed within the medium, which, as a result of a defrosting event, is able to undergo a displacement relative to the housing and therefore indicate a change of state of the medium. The freezable medium may be water, and the indicator may be a ball bearing. The housing may include a transparent phial 12 with associated end caps 14 to provide an hermetic seal. The phial may be secured to a backing plate 20 via a clip 22, and the reverse of the backing plate may include an adhesive pad 24 for fixing the device to the interior of a freezer compartment. The device is simple to install and provides a reliable and effective visual aid to ascertain immediately whether foodstuffs within a freezer have defrosted and subsequently been re-frozen as a result of a freezer malfunction or power outage etc.

Description

A FREEZER GUARD

The present invention relates to safety devices for freezers and freezer compartments, and in particular to a device for indicating the occurrence of defrosting events.

The use of freezers and refrigerators having integral freezer compartments is now commonplace within domestic environments. Almost every modern home has at least one appliance that enables foodstuffs to be frozen and stored to thereby extend the lifetime of the food. The technique of freezing food has long been known to prevent or inhibit the growth of bacteria and mould, that otherwise would eventually lead to the decay of the food and may also render the food potentially unsafe to eat.

Therefore, it is very important when storing frozen foodstuffs to ensure that the foodstuffs are constantly maintained in a frozen state, to avoid the possibility of any bacteria or fungi developing. However, although modern freezer appliances are relatively reliable and stable in operation, they are susceptible to occasional malfunction and to power outages, for example, prolonged power cuts etc. Many freezers and freezer compartments are able to maintain foodstuffs in a frozen state for several or more hours in the event of a power outage, due to thick insulation surrounding the freezer compartment. But if the power outage is lengthy, the foodstuffs will inevitably begin to defrost and thaw out, which increases the risk of bacteria developing due to the increase in ambient temperature.

It is known that certain foodstuffs, such as meat and fish etc., are more prone to bacterial contamination than say, fruit and vegetables. Therefore, it is important to know whether any defrosting of the foodstuffs has occurred during a power outage. If an individual is at home during the power outage, they will be able to monitor the foodstuffs directly by periodically checking whether or not the foodstuffs are still frozen. In this way, the individual is then able to exercise their judgement as to whether to keep, or subsequently discard, the food. However, should the individual be at work or on holiday etc., they may not have any idea that a power outage has actually occurred, or if so what the duration was, and consequently on their return they may be at risk of eating food harbouring potentially harmful bacteria. This issue is of particular concern where the power to the freezer has been restored following complete or partial thawing of the foodstuffs, as for example, meat and fish may become contaminated with bacteria, such as salmonella or listeria, as result of defrosting and re-freezing. Since the foodstuffs have subsequently refrozen, an individual may not recognise that any problem has arisen and therefore would likely be unaware of the potential risk to their health.

The prior art has addressed the issue of monitoring the status of freezers and of warning individuals as to temperature variations in freezer compartments, by providing specially designed thermometers. These thermometers are typically digital devices that sound an audible alarm and/or modulate a visual indicator (e.g. LED) if the temperature in the freezer increases above a pre-set threshold level. Such devices usually employ some form of probe or sensor that is located within the freezer compartment and which is connected to a display unit external to the freezer. The display unit may include a digital readout device, such as an LCD display, which allows an individual to view the temperature within the freezer compartment.

Although such digital thermometers provide an effective technique of both monitoring the temperature within a freezer compartment and of alerting an individual as to a temperature rise within the compartment, they are known to have several disadvantages associated with their widespread use. For instance, installing the probe and display unit may be troublesome for some individuals, as the electrical leads usually need to pass via the connecting seal between the compartment door and freezer frame. Moreover, in so doing, the integrity of the seal may therefore be diminished, which can reduce the overall efficiency of the freezer and may lead to further power consumption.

Furthermore, digital thermometers are generally only effective if an individual is located nearby, as unless the individual is actually aware of the audible/visual warning they are unable to take steps to respond. It is known that some thermometers may retain information relating to a temperature increase, for example, by illuminating an LED, which can then be viewed (and re-set) by an individual on his/her return. However, such functionality does not generally indicate whether any of the foodstuffs within the freezer compartment have actually defrosted and undergone significant thawing, and therefore such thermometers may be of little use in establishing whether there is a potential health risk in consuming the affected food.

It is also usually the case that digital thermometers are relatively expensive devices, the cost of which may deter many homeowners from installing one in their appliances, particularly if they have more than one freezer, for example, a chest freezer and a freezer compartment in their refrigerator.

As a result, many homeowners may knowingly, or unknowingly, be taking unnecessary health risks with regards to spoilt' frozen foodstuffs.

According to the present invention there is provided a device to indicate the occurrence of a defrosting event within a freezer, the device comprising: a housing containing a freezable medium, the medium being able to change between a first, frozen state and a second, unfrozen state in response to a defrosting event; and an indicator disposed within the medium, which, as a result of a defrosting event, is able to undergo a displacement relative to the housing to thereby indicate a change of state of the medium.

The present invention seeks to address some or all of the above problems in the prior art by providing a cheap and simple device that provides a clear visual indication of whether a defrosting event has occurred in a freezer or freezer compartment. In this way, an individual is able to immediately determine whether any foodstuffs in the freezer have defrosted and undergone thawing, which then allows the individual to exercise his/her judgement as to whether to dispose of the food to avoid a potential risk to their health.

io References herein to freezer' or freezer compartment' are taken to include any form of appliance or part of an appliance that provides a volume or space in which the temperature may be reduced and maintained below the ambient temperature external to the appliance. In particular, the terms are intended to include all types of domestic freezers and is refrigerators having an internal freezer compartment, whether upright, frost-free' or chest varieties, in addition to industrial style freezers and freezer compartments.

The device of the present invention comprises a housing. The housing is preferably elongate in form and is most preferably a cylindrical hollow tube.

The tube is preferably sealed at either end using end caps or aperture stops, which are either friction-fit and/or glued in place. In preferred embodiments, the tube is hermetically sealed to prevent or inhibit the ingress of air, and to avoid leakage of the freezable medium.

The housing may be completely transparent or else may include a window' that extends along at least part of the length of the tube.

Alternatively, the housing may be translucent. In an exemplary embodiment, the housing is a transparent plastic phial.

The freezable medium is contained within the housing, and the medium is able to change from a first, frozen state to a second, unfrozen state in response to a defrosting event. In preferred embodiments, the freezable medium is water and, is most preferably, a relatively low oxygenated water. Preferably, the first state of the medium corresponds to the solid state of water, i.e. ice, while the second state of the medium corresponds to the liquid state of water, i.e. liquid water. Therefore, the medium is preferably able to change state from ice to liquid water in response to a defrosting event.

By defrosting event' we mean an event in which the relatively low temperature within the freezer compartment has ceased to be maintained and whereupon the conditions are such as to allow a change of state or phase of the freezable medium. In the case of water ice, such an event encompasses the transition of ice into liquid water, which may also correspond to the partial or complete defrosting or thawing of water within any foodstuffs stored in the freezer compartment.

The indicator is disposed within the medium and is arranged to undergo a displacement relative to the housing, as a result of a defrosting event.

Preferably, the indicator is a solid object, and is most preferably a ball bearing, that is sealed within the housing, along with the freezable medium.

The ball bearing may be brightly coloured and is preferably coated in a red plastic coating, to enhance its visibility through the medium and housing wall, and to also avoid any possibility of corrosion.

The device may further comprise a backing plate onto which the housing may be mounted. The backing plate is preferably made from a relatively stiff plastic. Any suitable shape backing plate may be used, of any appropriate thickness, but in preferred embodiments the plate is rectangular, which in use, is arranged to have its longest axis substantially aligned with the longitudinal axis of the housing.

Preferably, the backing plate includes markings on its surface that serve to define locations relative to the housing, against which the position of the indicator may be visually compared. The markings are preferably such that they define at least two reference levels, one located proximate to each end of the housing, which may be used to assess the degree of displacement of the indicator. In preferred embodiments, the uppermost level is denoted as SAFE', while the relatively lower level is denoted as UNSAFE'. Of course, any number of suitable markings and/or nomenclature may be used to reference the position of the indicator relative to the housing.

An attachment means is preferably secured to the backing plate in order to receive the housing. The attachment means may be any suitable releasable clip or clasp, releasable adhesive or temporary gripping mechanism, and in preferred embodiments is a snap-in cable clip.

Alternatively, the housing may be permanently mounted to the backing plate by way of a pivoting clip that is able to rotate the housing by up to degrees relative to the backing plate.

The backing plate may also have an adhesive means attached to its reverse side (i.e. side opposite to the housing), which allows the device to be secured to an interior surface of the freezer or freezer compartment.

Preferably, the adhesive means is an adhesive pad that is intended to adhere to a clear wall' of the freezer, i.e. a surface from which the ice and frost have been removed prior to fixing the device. However, it is to be appreciated that any other suitable means for fixing or securing the device within the interior of the freezer or freezer compartment may alternatively be used.

In use, the housing is preferably aligned so as to be substantially vertical, which is to say, that the longitudinal axis defined by the tube points upwards substantially along a direction that passes through the top of the freezer or freezer compartment. As a result, when the medium is in its unfrozen state, the indicator is free to move, under the action of its own weight, towards the bottom of the housing, which in the case of the ball bearing means the bearing passes through the liquid water, along the length of the tube, until it comes to rest at, or near, the bottom of the tube.

At this stage, an individual then preferably fixes the device within the freezer or freezer compartment to allow the medium to freeze, such that it changes from an unfrozen state to a frozen state, e.g. liquid water to ice.

Depending on the particular freezer and temperature within the freezer compartment, the medium may take several hours until it becomes fully frozen. Once the medium freezes (i.e. solidifies), the indicator becomes fixed within the frozen medium and consequently is prevented from moving within the housing.

In order to configure the device to monitor for defrosting events, the individual preferably unclips the housing from the backing plate and inverts it relative to the housing. In this way, the indicator is then located near the top of the housing, which may then be re-attached to the backing plate via the releasable clip. In embodiments where the clip is pivotable, an individual may alternatively rotate the housing about the pivot by around degrees, so that the housing is thereby inverted.

Preferably, once the housing has been inverted the device is ready for use and can be left unattended within the freezer or freezer compartment. As the device is a completely self-contained unit, no electrical connections or other connecting means are required to be passed via the freezer seal, which advantageously avoids any loss of integrity in the seal. Moreover, as the operation of the device is principally dependent on a phase change of the medium, no power source is required for the device. Therefore, the device is environmentally friendly and is not dependent on cells or batteries etc. As a result, the device can be left indefinitely within the freezer, until such time as it needs to be re-set' following a defrosting event.

Preferably, the individual periodically checks the device by opening the freezer compartment (e.g. freezer door) and visually inspecting the position of the indicator. How often an individual checks the device will depend on personal preference, but it is expected that an individual would check the device if they had been away from their home for any length of time and/or if they suspected that a power outage had occurred.

If at some point in time a power outage does occur, leading to a defrosting event, the temperature within the freezer or freezer compartment will begin to rise and, if the outage is prolonged, the medium within the housing will then gradually change from a frozen state to an unfrozen state. Where the medium is water, the frozen ice within the housing will consequently thaw and melt as it reverts back into liquid water, which thereby releases the previously trapped indicator. Since the indicator has mass, it will undergo a vertical displacement relative to the housing, under the action of its own weight. Therefore, the indicator will pass substantially along the vertical axis of the housing, from a first level, near to the top of the housing, to a lower level at, or near, the bottom of the housing.

When the power outage ends, and power is eventually restored to the freezer, the temperature within the freezer compartment will decrease, thereby allowing the compartment to re-freeze, which in turn causes the medium within the housing to change from an unfrozen to a frozen state once again. In so doing, the medium solidifies and traps the indicator at the bottom of the housing.

At a subsequent time, when the individual checks the device, he/she will immediately notice that the indicator is now located at the bottom of the housing, thereby indicating that a defrosting event has occurred within the freezer or freezer compartment. Since the indicator was able to pass from the top to the bottom of the housing, the individual will understand that the conditions were such within the freezer for the medium to change from ice into liquid water, which consequently implies that any foodstuffs within the compartment will have also undergone a partial or complete thawing.

Hence, the individual can then exercise his/her judgement as to whether to dispose of the food on the grounds that it may now pose a possible health risk to their well-being.

In order to re-set' the device, the individual may now simply unclip the housing from the backing plate, invert it and re-attach it to the plate, so that the indicator is once again located near to the top of the plate.

Alternatively, where a pivoting clip is used, the housing can simply be rotated through 180 degrees.

There are a number of modifications that may be made to the above invention without sacrificing any of the functionality or advantages associated with the present device. For example, instead of using a backing plate, the housing may be fabricated so as to be self-standing, in that the end caps have a flat surface enabling them to stand on a horizontal surface within the freezer or freezer compartment. In this case, the end caps may be suitably flared so as to increase the stability of the device within the freezer compartment. The housing itself could then be marked with suitable universal reference levels and/or wording, with which to compare the position of the indicator.

In alternative embodiments, the indicator may be in the form of a liquid instead of a ball bearing. The liquid is selected to have a density which is different to that of the density of the medium when it is unfrozen. For example, where the medium is water, the liquid may be selected to have a density that is either greater than or less than the density of liquid water.

If the liquid indicator has a density that is greater than the liquid water, then when the ice melts into water, as a result of a defrosting event, the liquid indicator will then descend through the water and towards the bottom of the housing. Alternatively, if the liquid indicator has a density that is lower than that of liquid water, it will then rise upwardly towards the top of the housing, due to buoyant forces acting on the indicator. In either case, the different densities between the medium and indicator create a pressure gradient that acts to displace the liquid relative to the housing during a defrosting event.

In the case where the liquid indicator is less dense than liquid water, it is to be appreciated that the method of use described above is adapted accordingly, in the sense that, should an individual notice that the indicator is now at the top of the housing, he/she will know that a defrosting event has occurred in the freezer or freezer compartment.

The liquid indicator may be a coloured dye, oil or other suitable liquid, and is at least partially immiscible with liquid water.

In other embodiments, the indicator may alternatively be a plastic ball or relatively short cylinder (i.e. shorter in length than the housing), which is able to rise upwards through the housing in response to a defrosting event, as a result of its inherent natural buoyancy within the liquid water. To further enhance buoyancy, the ball or cylinder may be hollow and filled with air to facilitate the displacement of the indicator as the water ice begins to thaw.

It is to be understood that in each of the above embodiments, the quantity of unfrozen medium (e.g. water) inserted into the housing is such that a small volume of air is left within the housing to allow for expansion of the medium as it changes to its solid state (e.g. ice).

Although the above embodiments have been described with reference to a cylindrical hollow tube, it should be appreciated that the housing may have any other suitable shape and/or cross-sectional profile, depending on the particular indicator used and desired application.

Embodiments of the invention will now be described in detail by way of example and with reference to the accompanying drawings in which: Figure 1 is a perspective view of a particularly preferred embodiment of a device according to the present invention.

Figure 2 is a schematic view illustrating the setting of a device according to a preferred embodiment of the invention.

Figure 3 is a schematic view illustrating the operation of the device as shown in Figure 2.

Referring to Figure 1, there is shown a particularly preferred embodiment of the device 10 according to the present invention. The device 10 comprises a housing in the form of a cylindrical phial 12, hermetically sealed at either end by caps 14. The caps 14 are friction fit to the phial 12 and are sealed by a water-proof adhesive.

The phial 12 is fabricated from plastic and is completely transparent.

Alternatively, the phial 12 may be made from glass. The phial 12 is dimensioned such that it is 60 mm in length and 8 mm in diameter. The end caps 14 are either made from plastic or hardened rubber.

Contained within the phial 12 is a low oxygenated water 16 that is able to undergo a phase change into ice when the device 10 is placed within a freezer or freezer compartment, and back again into liquid water in response to a defrosting event.

The device 10 further comprises an indicator in the form of a steel ball bearing 18. The ball bearing 18 is disposed within the water 16 inside of the phial 12. To enhance visual identification of the ball bearing 18, and to avoid any possible corrosion, it is coated with a thin layer of red plastic or rubber. Alternatively, the ball bearing 18 may be painted with a brightly coloured paint or varnish. The ball bearing is about 4-6 mm in diameter.

Referring again to Figure 1, the phial 12 is attached to a backing plate 20.

The backing plate 20 is a rectangular plate having dimensions of height 70 mm x width 50 mm x thickness 1mm. For durability and ease of fabrication, the backing plate 20 is made from a relatively stiff plastic.

A releasable clip 22 is fixed to the backing plate 20, so as to receive the phial 12. The clip 22 is a snap-fit cable clip having an internal diameter sufficient to resiliently grip the phial 12, as shown in Figure 1. The use of a releasable clip is advantageous, as it allows the phial 12 to be easily removed from, and be re-attached to, the backing plate 20 as required.

The clip 22 is fixed to the backing plate 20 by way of an adhesive, but may alternatively be thermally bonded or screwed in place.

On the reverse side of the backing plate 20, i.e. the side opposite to that of the phial 12, there is located an adhesive pad 24 for fixing the device 10 to an interior surface of the freezer or freezer compartment. The adhesive pad is of conventional design and is dimensioned according to the size of the backing plate 20. There may be more than one pad 24 depending on the particular application and bonding strength required.

As shown in Figure 1, the backing plate 20 also includes two reference levels 26, 28, denoted as SAFE' and UNSAFE' respectively. The reference levels 26, 28 serve as permanent markers against which the position of the ball bearing 18 may be compared during use of the device 10. To further enhance the visual impression made by the reference levels 26, 28, each marker may be printed in an appropriate colour. Therefore, the SAFE' marker can be printed in green bold font, while the UNSAFE' marker can alternatively be printed in red bold font, to further emphasis the potential risk involved in consuming any foodstuffs that have been subjected to a defrosting event.

Referring now to Figure 2, there is shown an example of the procedure involved in configuring the device 10 for use in the freezer or freezer compartment. For clarity of presentation, only part of the device 10 is shown. However, it is to be appreciated that the discussion with respect to Figure 2 applies to the whole device and not just to the illustrated components.

In Figure 2(a), the device 10 is shown prior to use, e.g. before installation of the device or prior to the freezer being turned on. In this state, the water 16 is liquid, and with the phial 12 being held upright, the ball bearing 18 is at rest at the bottom of the phial 12. The device 10 is then fixed inside of the freezer and is allowed to experience a period of freezing, whereupon the water 16 turns to water ice. In so doing, the ball bearing 18 is now trapped at the bottom of the phial 12 and is consequently unable to move relative to the phial 12.

In order to set' the device 10, an individual unclips the phial 12 from the releasable clip 22 and proceeds to invert the phial 12, before re-attaching it to the clip 22. As a result, the ball bearing 18 is now at the top of the phial 12 and has a position which corresponds approximately to the SAFE' marker 26 on backing plate 20, as shown in Figure 2(b). The device 10 is now ready to monitor for defrosting events.

Referring now to Figure 3, there is shown an example of the operation of the device 10 at a subsequent time when a defrosting event occurs. In the same way as for Figure 2, only part of the device 10 is shown for clarity.

However, it is to be appreciated that the discussion with respect to Figure 3 applies to the whole device and not just to the illustrated components.

In a response to a defrosting event, the temperature within the freezer or freezer compartment increases, causing the water ice within the phial 12 to gradually melt into liquid water. As a result, the ball bearing 18 is displaced downwards, under the action of its own weight (see Figure 3(a)), until it comes to rest at the bottom of the phial 12, as shown in Figure 3(b).

Once power is restored to the freezer, the temperature within the freezer compartment will decrease, allowing the water 16 to once again freeze into ice, thereby trapping the ball bearing 18 at the bottom of the phial 12.

Upon later inspection, an individual is then able to immediately recognise that the ball bearing 18 is now located adjacent to the UNSAFE' marker 28 on the backing plate 20, which thereby indicates to the individual that a defrosting event has occurred and that conditions were such as to temporarily allow water ice to revert back into a liquid state. Having knowledge of this fact, the individual may then exercise his/her judgement as to whether to dispose of any affected foodstuffs, given that is was quite likely that the food had partially or completely thawed out before being re-frozen.

In order to re-set' the device 10, the individual can simply unclip the phial 12, invert it and then re-attach it to the clip 22. In this way, the ball bearing 18 is once again located at the top of the phial 12 and is adjacent to the SAFE' marker on backing plate 20. The device 10 is then again ready to monitor for defrosting events.

It is to be appreciated therefore that the present invention provides a very simple device for reliably and effectively monitoring for defrosting events in freezers and freezer compartments, which does not require any skill to install nor has any complex display to interpret, and yet provides an unambiguous visual alert, while being cheap and easy to manufacture.

The above embodiments are described by way of example only. Many variations are possible without departing from the invention.

Claims (16)

1. CLAIMS1. A device to indicate the occurrence of a defrosting event within a freezer, the device comprising: a housing containing a freezable medium, the medium being able to change between a first, frozen state and a second, unfrozen state in response to a defrosting event; and an indicator disposed within the medium, which, as a result of a defrosting event, is able to undergo a displacement relative to the housing to thereby indicate a change of state of the medium.
2. 2. The device as in Claim 1, wherein the displacement relative to the housing is substantially along a vertical axis of the housing.
3. 3. The device as in Claim 1 or Claim 2, wherein the displacement is from a first, higher level to a second, relatively lower level.
4. 4. The device as in any preceding claim, wherein the indicator is displaced under the action of its own weight.
5. 5. The device as in preceding claim, wherein the housing is configured to be invertible so as to allow the position of the indicator to be re-set.
6. 6. The device as in any preceding claim, wherein the housing is hermetically sealed.
7. 7. The device as in any preceding claim, wherein the housing is substantially transparent.
8. 8. The device as in any preceding claim, wherein the housing is a phial.
9. 9. The device as in any preceding claim, wherein the indicator is a ball bearing.
10. 10. The device as in Claim 1 or Claim 2, wherein the indicator is a liquid having a density different to that of the density of the medium when in its second state.
11. 11. The device as in Claim 10, wherein the different densities create a pressure gradient that acts to displace the liquid relative to the housing during a defrosting event.
12. 12. The device as in any preceding claim, wherein the medium is water.
13. 13. The device as in any preceding claim, further comprising a backing plate onto which the housing is mountable.
14. 14. The device as in Claim 13, further comprising an attachment means for mounting the housing to the backing plate.
15. 15. The device as in any preceding claim, further comprising an adhesive means for securing the device to an interior surface of the freezer.
16. 16. A device as substantially described herein with reference to the accompanying drawings.