AN ELECTRICAL PLUG AND AN ELECTRICAL RECEPTACLE

Field

5 The present invention relates to electrical plugs and sockets.

Background to the invention

Over half of accidental domestic fires in the UK are electrical, typically due to misuse or faults.

10 For example, overloading of a socket and/or damage and/or wear thereto may cause resistive heating thereof, resulting in a fire. For example, overloading of a plug and/or damage and/or wear thereto may cause resistive heating thereof, resulting in a fire.

Hence, there is a need to improve safety to prevent such fires.

15

Summary of the Invention

It is one aim of the present invention, amongst others, to provide a safety element which at least partially obviates or mitigates at least some of the disadvantages of the prior art, whether

20 identified herein or elsewhere. For instance, it is an aim of embodiments of the invention to provide a safety element that mutually electrically isolates a plug and a socket upon overheating thereof.

A first aspect provides a safety element disposable between a plug and a socket, the safety

25 element comprising a thermal expansion member; wherein the safety element is configurable in: a first configuration, wherein the safety element is disposed between the plug and the socket and wherein the safety element has a first thickness, whereby the plug and the socket are mutually electrically coupled; and

30 a second configuration, wherein the safety element is disposed between the plug and the socket and wherein the safety element has a second thickness greater than the first thickness, whereby the plug and the socket are mutually electrically uncoupled; wherein the safety element is configured to move from the first configuration to the second configuration upon heating of the thermal expansion member to or above a threshold

35 temperature.

A second aspect provides an assembly comprising a safety element according to the first aspect, a plug and a socket or a faceplate thereof. A third aspect provides a kit of parts comprising a safety element according to the first aspect and a plug and/or a socket or a faceplate thereof.

A fourth aspect provides a plug comprising a safety element according to the first aspect.

A fifth aspect provides a socket comprising a safety element according to the first aspect.

A sixth aspect provides an adaptor comprising a safety element according to the first aspect

A seventh aspect provides a method of mutually electrically uncoupling a plug and a socket upon heating to or above a threshold temperature, the method comprising: configuring a safety element, comprising a thermal expansion member, in a first configuration, wherein the safety element is disposed between the plug and the socket and wherein the safety element has a first thickness, whereby the plug and the socket are mutually electrically coupled; and moving the safety element from the first configuration to a second configuration by heating the thermal expansion member to or above the threshold temperature, wherein the safety element is disposed between the plug and the socket and wherein the safety element has a second thickness greater than the first thickness, whereby the plug and the socket are mutually electrically uncoupled.

Detailed Description of the Invention

According to the present invention there is provided a safety element, as set forth in the appended claims. Also provided is an assembly, a kit of parts, a plug, a socket or a faceplate thereof, an adaptor and a method. Other features of the invention will be apparent from the dependent claims, and the description that follows.

Safety element

The first aspect provides a safety element disposable between a plug and a socket, the safety element comprising a thermal expansion member; wherein the safety element is configurable in: a first configuration, wherein the safety element is disposed between the plug and the socket and wherein the safety element has a first thickness, whereby the plug and the socket are mutually electrically coupled; and a second configuration, wherein the safety element is disposed between the plug and the socket and wherein the safety element has a second thickness greater than the first thickness, whereby the plug and the socket are mutually electrically uncoupled; wherein the safety element is configured to move from the first configuration to the second configuration upon heating of the thermal expansion member to or above a threshold temperature.

In this way, upon heating of the thermal expansion member to or above the threshold temperature, the safety element moves from the first configuration to the second configuration, thereby urging the plug away from the socket as the thickness of the safety element increases from the first thickness to the second thickness and in turn, mutually electrically uncoupling the plug and the socket. In other words, the safety element unplugs the plug from the socket, sufficiently to electrically disconnect the plug from the socket. By mutually electrically uncoupling the plug and the socket, transmission of electrical power from the socket to the plug is interrupted, thereby preventing further heating due to the electrical power and/or electrically isolating the plug and thus switching off an electrical device electrically connected thereto. That is, the safety element mutually electrically isolates the plug and the socket upon overheating thereof. In this way, a fire and/or damage may be avoided.

Since the safety element is configured to move from the first configuration to the second configuration upon heating of the thermal expansion member to or above the threshold temperature, such movement may be in response to at least three scenarios:

1 . overloading of the socket and/or damage and/or wear thereto, causing resistive heating thereof and heating of the thermal expansion member to or above the threshold temperature in turn; and/or

2. overloading of the plug and/or damage and/or wear thereto, causing resistive heating thereof and heating of the thermal expansion member to or above the threshold temperature in turn; and/or

3. an external heat source, such as a fire in the room, causing heating of the thermal expansion member to or above the threshold temperature in turn.

In each scenario, transmission of electrical power from the socket to the plug is interrupted, thereby preventing further heating due to the electrical power and/or electrically isolating the plug and thus switching off an electrical device electrically connected thereto. In this way, a fire and/or damage may be avoided.

That is, the safety element behaves as or is a thermal overload or trip and/or a circuit breaker. Equivalently, alternatively and/or additionally, the first aspect provides a safety element disposable between a plug and a socket, the safety element comprising a thermal expansion member, wherein the safety element is configured to urge apart the plug and the socket upon heating of the thermal expansion member to or above a threshold temperature, thereby mutually electrically uncoupling the plug and the socket.

Plug and socket

Plugs and sockets (also known as outlets) are known. Conventionally, in use, a plug and a socket (i.e. a matching or mating socket) mutually contact or confront (for example, a base of the plug and a faceplate of the socket mutually contact or confront), whereby the plug and the socket are mutually electrically coupled, via a set of pins (also known as blades or connectors) (i.e. male members) of the plug inserted into a set of receptacles (i.e. female members) of the socket.

Typically, mutual electrical coupling requires that the set of pins of the plug are inserted by at least a minimum depth of insertion (for example, 15 to 20 mm) into the set of receptacles of the socket, for example delimited by a relatively longer earth pin of the set thereof, the set of pins of the plug having electrically conducting tips only and/or the set of receptables having electrically conducting bottoms only. The minimum depth of insertion improves safety and provides mechanical stability. Typically, a maximum depth of insertion (for example, 20 to 25 mm) is defined by a base of the plug and a faceplate of the socket mutually contacting. Hence, mutual electrical coupling of the plug and the socket results when the set of pins of the plug are inserted into the set of receptacles of the socket to between the minimum depth of insertion and the maximum depth of insertion. In other words, a range of depth of insertion, between the minimum depth of insertion and the maximum depth of insertion, is tolerated for mutual electrical coupling of the plug and the socket. In contrast, the plug and the socket are mutually electrically uncoupled when the set of pins of the plug are inserted into, or withdrawn from, the set of receptacles of the socket to less than the minimum depth of insertion.

In one example, the plug and the socket are an AC power plug and an AC power socket, respectively, for example Type A, Type B, Type C, Type D, Type E, Type F, Type G, Type H, Type I, Type J, Type K, Type L, Type M or Type N (i.e. for domestic applications). Other standards are known.

In one example, the plug comprises and/or is an adaptor, for example a travel adaptor or a multi-plug adaptor.

Safety element The safety element (also known as a protective device) is disposable (i.e. receivable) between the plug and the socket. It should be understood that, in use, the safety element is disposed between the plug and the socket, for example spacing apart the plug and the socket by the first distance or the second distance. It should be understood that the safety element is specifically adapted for use with the plug and the socket, for example dimensioned and/or shaped to be disposed therebetween without affecting normal function of the plug and the socket, in the first configuration. It should be understood that the safety element is an electrical insulator and optionally, a thermal insulator. It should be understood that the safety element is a passive safety element, activated by heat only.

In one example, the safety element has a first face and a second face, wherein the first face and the second face are mutually opposed, wherein the first face is arranged to contact or confront the plug, for example a base thereof, and wherein the second face is arranged to contact or confront the socket, for example a faceplate thereof, or vice versa. In one example, the first face and/or the second face is provided by the thermal expansion member. In this way, the thermal expansion member directly contacts or confronts the plug, for example a base thereof, and/or the socket, for example a faceplate thereof.

In one example, the safety element comprises a substrate having the thermal expansion member arranged (i.e. located, positioned) thereon and/or therein, for example as a first layer (i.e. the substrate) and as a third layer (i.e. the thermal expansion member), respectively. In this way, a mechanical robustness of the safety element is improved. In one example, the first face is provided by the substrate and the second face is provided by the thermal expansion member. In this way, the substrate directly contacts or confronts the plug, for example a base thereof, and the thermal expansion member directly contacts or confronts the socket, for example a faceplate thereof, or vice versa. In one example, the substrate comprises a fibrous material (for example paper, card, woven or non-woven textile) and/or a polymeric composition comprising a polymer (for example, a thermoplastic, such as PTFE, PVC, PP).

In one example, the safety element comprises a housing having a first wall and a second wall, wherein the first wall and the second wall are mutually opposed, and wherein the thermal expansion member is arranged (i.e. located, positioned) between, for example wholly between, the first wall and the second wall, for example as a first layer (i.e. the first wall), as a third layer (i.e. the thermal expansion member) and as second layer (i.e. the second wall), respectively. In one example, the first face is provided by the first wall and the second face is provided by the second wall. In this way, the first wall and hence the housing directly contacts or confronts the plug, for example a base thereof, and the second wall and hence the housing directly contacts or confronts the socket, for example a faceplate thereof, or vice versa. In one example, the housing has a side wall between the first wall and the second wall, wherein the thermal expansion member is enclosed (for example contained, sealed, hermetically sealed, encapsulated) within, for example wholly within, the housing. In this way, the thermal expansion member is not exposed and/or the thermal expansion member is contained within the housing upon moving from the first configuration to the second configuration. In one example, the housing comprises and/or is an expandable housing, for example having an extensible or deformable side wall, such as a resilient side wall and/or a concertina (i.e. foldable) side wall, for example provided by a blister pack or a bubble pack having one or more (i.e. a plurality) of blisters or bubbles, respectively, or bellows, for example. In this way, a dimension, for example a thickness, of the housing may be expanded, for example upon moving from the first configuration to the second configuration. In one example, the housing comprises a fibrous material (for example paper, card, woven or non-woven textile) and/or a polymeric composition comprising a polymer (for example, a thermoplastic, such as PTFE, PVC, PP, which softens upon heating and allows expansion of the housing).

In one example, the safety element comprises and/or is a sheet, a laminate, a pad, a washer or a gasket. That is, the safety element is planar, having a relatively small first thickness compared with a width and/or a length thereof. In this way, the safety element may be configured in the first configuration. In one example, the safety element is in the form of a sheet, a laminate, a pad, a washer or a gasket.

In one example, a perimeter of the safety element conforms with a perimeter of the plug, for example wherein the perimeter of the safety element is within the perimeter of the plug. In this way, the safety element is dimensioned compatibly with the plug, facilitating use and/or not obstructing a switch of the socket, for example. In one example, the perimeter of the safety element is wholly within the perimeter of the plug. In this way, the safety element is not obtrusive, at least in the first configuration. In one example, the perimeter of the safety element is partly within the perimeter of the plug, for example having a tab extending away from the plug. In this way, presence or absence of the safety element may be readily observed, by inspection, without withdrawing the plug from the socket, for example. In one example, a shape of the safety element is similar to a shape of the plug, for example circular, triangular, square, rectangular or hexagonal. Other shapes are known. In this way, the safety element is shaped compatibly with the plug, facilitating use and/or not obstructing a switch of the socket, for example.

In one preferred example, the safety element has a shape and dimensions, including the first thickness, similar to or the same as a wiring safety diagram card, such as included on a new plug. Thermal expansion member

The safety element comprises the thermal expansion member.

In one example, the thermal expansion member comprises and/or is an intumescent, a bimetallic strip, a disbondable adhesive having a disbonding temperature corresponding to the threshold temperature, a solid having a sublimation point corresponding to the threshold temperature and/or a liquid having a boiling point corresponding to the threshold temperature.

Generally, an intumescent is a material that swells (generally irreversibly) as a result of heat exposure, thus leading to an increase in volume and decrease in density. Soft char intumescents produce a light char, which is a poor conductor of heat, thus retarding heat transfer but the expansion pressure that is created for soft char intumescents is relatively low. In contrast, hard char intumescents produce a char capable of exerting a relatively high expansion pressure. Hard char intumescents, typically comprising sodium silicates and graphite, are preferred. Optionally, the intumescent is enclosed in an expandable housing (i.e. an encapsulation) of the safety element. Hence, the safety element moves from the first configuration to the second configuration due to the swelling of the intumescent.

Suitable intumescents include: ammonium phosphate; hydrated sodium silicate; intercalated graphite; and mixtures thereof. Ammonium phosphate intumescents were originally based on mono-ammonium phosphate (often abbreviated to MAP) but ammonium polyphosphate (APP) has also been used recently. Ammonium phosphate intumescents have an activation temperature of about 180°C and typically generate large volumes of protective foam accompanied by relatively low pressure generation. Ammonium phosphate intumescents are available as sheets and strips and as additives for pastes, mastics and paints. Hydrated sodium silicate intumescents have a relatively low activation temperature in the region 110°C to 120°C, moderate expansion volume accompanied by relatively high pressure generation, and provide a hard, mechanically stable foam, with excellent thermal insulation properties. Reinforcements such as glass fibres are common, adding to the stability, and resulting in a relatively more uniaxial expansion, if preferred. The hydrated nature of these materials enables a significant cooling effect to be achieved. Hydrated sodium silicate intumescents are available as sheets and strips and as additives. Intercalated graphite differs from ordinary graphite in having water molecules sandwiched between the layers of carbon. On heating, the water is turned into steam causing the graphite to exfoliate, producing a light 'fluffy' material. During the expansion phase, relatively high pressure generation may be obtained if the expansion is restricted, and the resulting material will typically be compacted but spongy. Activation temperatures of intercalated graphite are generally in the region of 170°C to 200°C. Intercalated graphite intumescents are available in a pre-compounded form within a flexible PVC matrix or incorporated into mineral fibre composites.

Generally, a bimetallic strip is used to convert a temperature change into a mechanical displacement and typically comprises two strips of different metals which expand at different rates as they are heated. The differential expansion causes an initially flat strip to bend in one direction when heated and in the opposite direction when cooled, reversibly. Hence, the safety element moves from the first configuration to the second configuration due to the differential expansion of the bimetallic strip.

Generally, a disbondable adhesive (also known as a debonding adhesive) has a disbonding temperature (also known as a debonding temperature) at which adhesion due thereto is significantly diminished, reversibly. By selecting a disbondable adhesive having a disbonding temperature corresponding (for example equal) to the threshold temperature, a resilient biasing member comprised in the thermal expansion member, for example, is released at the threshold temperature, such that the safety element moves from the first configuration to the second configuration.

Generally, sublimation is the reversible conversion between solid and gas phases of matter, with no intermediate liquid phase, thereby providing a significant increase in volume. Hence, for a solid having a sublimation point corresponding to the threshold temperature (for example equal) and enclosed in an expandable housing of the safety element, the safety element moves from the first configuration to the second configuration due to sublimation of the solid.

Generally, boiling is the reversible conversion between liquid and gas phases of matter, thereby providing a significant increase in volume. Hence, for a liquid having a boiling point corresponding to the threshold temperature (for example equal) and enclosed in an expandable housing of the safety element, the safety element moves from the first configuration to the second configuration due to boiling of the liquid.

In one example, the thermal expansion member comprises a resilient biasing member, for example configured to urge apart the plug and the socket upon heating of the thermal expansion member to or above a threshold temperature.

First configuration

The safety element is configurable in the first configuration, wherein the safety element is disposed between the plug and the socket and wherein the safety element has the first thickness, whereby the plug and the socket are mutually electrically coupled. It should be understood that if the safety element contacts the plug and the socket in the first configuration, the plug and the socket are mutually spaced apart by the first thickness of the safety element. Hence, it should be understood that the plug and the socket are mutually spaced apart by at least the first thickness of the safety element, in the first configuration.

Since the plug and the socket are mutually electrically coupled in the first configuration when the safety element, having the first thickness, is disposed therebetween, the safety element does not affect normal function of the plug and the socket. Hence, the safety element may be retrofitted to existing plugs and/or sockets, without affecting normal operation thereof, thereby improving safety.

It should be understood that the first thickness is compatible with the range of depth of insertion, between the minimum depth of insertion and the maximum depth of insertion, for mutual electrical coupling of the plug and the socket, as described previously. An upper limit of the first thickness may be readily determined for the plug and the socket, for example by measurement, as understood by the skilled person.

In one example, the first thickness is in a range from 100 pm to 3 mm, preferably in a range from 250 pm to 2 mm, more preferably in a range from 500 pm to 1 mm. In this way, the safety element, configured in the first configuration, does not affect normal function of the plug and the socket.

Second configuration

The safety element is configurable in the second configuration, wherein the safety element is disposed between the plug and the socket and wherein the safety element has the second thickness greater than the first thickness, whereby the plug and the socket are mutually electrically uncoupled. It should be understood that if the safety element contacts the plug and the socket in the second configuration, the plug and the socket are mutually spaced apart by the second thickness of the safety element. Hence, it should be understood that the plug and the socket are mutually spaced apart by at least the second thickness of the safety element, in the second configuration.

Since the plug and the socket are mutually electrically uncoupled in the second configuration when the safety element, having the second thickness, is disposed therebetween, the safety element does affect normal function of the plug and the socket. It should be understood that the second thickness is incompatible with the range of depth of insertion, between the minimum depth of insertion and the maximum depth of insertion, for mutual electrical coupling of the plug and the socket, as described previously. A lower limit of the second thickness may be readily determined for the plug and the socket, for example by measurement, as understood by the skilled person.

In one example, the second thickness is in a range from 3 mm to 15 mm, preferably in a range from 4 mm to 10 mm, more preferably in a range from 5 mm to 8 mm. In this way, the safety element, configured in the second configuration, does affect normal function of the plug and the socket.

In one example, the safety element is configured to remain in the second configuration upon cooling of the thermal expansion member below the threshold temperature. That is, moving from the first configuration to the second configuration is irreversible, for example wherein the thermal expansion member comprises and/or is an intumescent and/or a resilient biasing member. In this way, the plug may not be reinserted into the socket upon cooling below the threshold temperature, thereby improving safety.

Moving

The safety element is configured to move from the first configuration to the second configuration upon heating of the thermal expansion member to or above a threshold temperature. In this way, upon heating of the thermal expansion member to or above the threshold temperature, the safety element moves from the first configuration to the second configuration, thereby urging the plug away from the socket as the thickness of the safety element increases from the first thickness to the second thickness and in turn, mutually electrically uncoupling the plug and the socket.

In one example, the safety element is configured to irreversibly move from the first configuration to the second configuration upon heating of the thermal expansion member to or above a threshold temperature. In this way, the plug may not be reinserted into the socket upon cooling below the threshold temperature, thereby improving safety.

In one example, the safety element is configured to reversibly move from the first configuration to the second configuration upon heating of the thermal expansion member to or above a threshold temperature. In this way, the plug may be reinserted into the socket upon cooling below the threshold temperature, for example following remedial action. In one example, the threshold temperature is in a range from 50 °C to 200 °C, preferably in a range from 55 °C to 175 °C, more preferably in a range from 50 °C to 85 °C. In this way, the threshold temperature is compatible with 60 °C, 75 °C and 90 °C thermoplastic cable or wire insulation and/or with 90 °C and 180 °C thermosetting cable or wire insulation. Table 1 shows Maximum Operating Temperatures according to National Electrical Contractor (NEC) Table 310-16. Other standards are known. Permissible transient temperatures may be higher.

Table 1 : Maximum Operating Temperatures according to NEC Table 310-16 Allowable Ampacities of Insulated Conductors.

In one example, a difference between the first thickness and the second thickness is in a range from 1 mm to 15 mm, preferably in a range from 2 mm to 10 mm, more preferably in a range from 3 mm to 8 mm. In this way, an increase in thickness of the safety element from the first thickness to the second thickness urges the plug away from the socket.

In one example, a ratio of the second thickness to the first thickness is in a range from 2 : 1 to 100 : 1 , preferably in a range from 3 : 1 to 50 : 1 , more preferably in a range from 4 : 1 to 10 : 1 . In this way, the second thickness is relatively large compared with the first thickness.

In one example, a force exerted by the safety element on the plug and/or the socket (i.e. a force exertable by the safety element) upon moving from the first configuration to the second configuration is in a range from 1 N to 100 N, preferably in a range from 5 N to 50 N, more preferably in a range from 10 N to 25 N. In this way, the safety element forcibly urges the plug away from the socket.

In one example, a pressure exerted by the safety element on the plug and/or the socket (i.e. a pressure exertable by the safety element) upon moving from the first configuration to the second configuration is in a range from 1 kPa to 250 KPa, preferably in a range from 5 kPa to 100 kPa, more preferably in a range from 10 kPa to 50 kPa. In this way, the safety element forcibly urges the plug away from the socket.

In one example, the safety element is configured to move uniaxially from the first configuration to the second configuration upon heating of the thermal expansion member to or above a threshold temperature. In this way, the thickness of the safety element increases from the first thickness to the second thickness, without corresponding increases (or substantial increases) in a width and/or a length of the safety element.

Perforations

In one example, the safety element comprises a set of perforations (also known as passageways, through holes or apertures), including a first perforation, therethrough correlating (i.e. aligned, optionally similarly shaped) with a set of pins of the plug. In this way, the set of pins of the plug may be inserted via the set of perforations of the safety element into the set of receptacles of the socket. In one example, the set of perforations includes the first perforation and a second perforation, for a two pin plug. In one example, the set of perforations includes the first perforation, a second perforation and a third perforation, for a three pin plug. It should be understood that when the safety element comprises a substrate and/or a housing, as described herein, the set of perforations extend through the substrate and/or the housing, for example between the first wall and the second wall of the housing. It should be understood that when the housing has a side wall, the side wall surrounds the set of perforations, for example as a bore thereof.

Attachment member

In one example, the safety element comprises an attachment member for attaching the safety element to the plug or to the socket. In this way, the safety element may be attached, for example secured, to the plug or to the socket, for example to only the plug or to only the socket. In this way, the safety element is retained on the plug or on the socket when the plug is withdrawn from the socket. In one example, the attachment member comprises and/or is an adhesive, for example a pressure sensitive adhesive, having a removable cover layer. In one example, the attachment member comprises and/or is lug or a plurality thereof, for example for clamping against an edge of the plug. In one example, the attachment member is provided by an interference fit between a set of perforations of the safety element, as described previously, and the set of pins of the plug.

Assembly

The second aspect provides an assembly comprising a safety element according to the first aspect, a plug and a socket or a faceplate thereof.

The plug may be as described with respect to the first aspect. In one example, the plug comprises and/or is an adaptor, for example a travel adaptor or a multi-plug adaptor. The socket may be as described with respect to the first aspect.

Kit of parts

The third aspect provides a kit of parts comprising a safety element according to the first aspect and a plug and/or a socket or a faceplate thereof.

The plug may be as described with respect to the first aspect. In one example, the plug comprises and/or is an adaptor, for example a travel adaptor or a multi-plug adaptor.

The socket may be as described with respect to the first aspect.

Plug

The fourth aspect provides a plug comprising a safety element according to the first aspect.

The plug may be as described with respect to the first aspect.

In one example, the safety element is provided on and/or in a base thereof.

Socket

The fifth aspect provides a socket comprising a safety element according to the first aspect.

The socket may be as described with respect to the first aspect.

In one example, the safety element is provided on and/or in a faceplate thereof.

Adaptor

The sixth aspect provides an adaptor comprising a safety element according to the first aspect

In one example, the safety element is provided on and/or in a base thereof.

Method

The seventh aspect provides a method of mutually electrically uncoupling a plug and a socket upon heating to or above a threshold temperature, the method comprising: configuring a safety element, comprising a thermal expansion member, in a first configuration, wherein the safety element is disposed between the plug and the socket and wherein the safety element has a first thickness, whereby the plug and the socket are mutually electrically coupled; and moving the safety element from the first configuration to a second configuration by heating the thermal expansion member to or above the threshold temperature, wherein the safety element is disposed between the plug and the socket and wherein the safety element has a second thickness greater than the first thickness, whereby the plug and the socket are mutually electrically uncoupled.

Definitions

Throughout this specification, the term “comprising” or “comprises” means including the component(s) specified but not to the exclusion of the presence of other components. The term “consisting essentially of’ or “consists essentially of’ means including the components specified but excluding other components except for materials present as impurities, unavoidable materials present as a result of processes used to provide the components, and components added for a purpose other than achieving the technical effect of the invention, such as colourants, and the like. The term “consisting of’ or “consists of’ means including the components specified but excluding other components. Whenever appropriate, depending upon the context, the use of the term “comprises” or “comprising” may also be taken to include the meaning “consists essentially of’ or “consisting essentially of’, and also may also be taken to include the meaning “consists of’ or “consisting of’.

The optional features set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. The optional features for each aspect or exemplary embodiment of the invention, as set out herein are also applicable to all other aspects or exemplary embodiments of the invention, where appropriate. In other words, the skilled person reading this specification should consider the optional features for each aspect or exemplary embodiment of the invention as interchangeable and combinable between different aspects and exemplary embodiments.

Brief description of the drawings

For a better understanding of the invention, and to show how exemplary embodiments of the same may be brought into effect, reference will be made, by way of example only, to the accompanying diagrammatic Figures, in which: Figure 1 is a CAD plan view of a safety element according to an exemplary embodiment;

Figure 2A is a CAD perspective view of the safety element of Figure 1 provided on a plug, wherein the safety element is configured in a first configuration; and Figure 2B is a CAD perspective view of the safety element of Figure 1 provided on the plug, wherein the safety element is configured in a second configuration;

Figure 3 schematically depicts AC power plugs and sockets for exemplary embodiments; and

Figure 4 schematically depicts a method according to an exemplary embodiment.

Detailed Description of the Drawings

Figure 1 is a CAD plan view of a safety element 10 according to an exemplary embodiment.

The safety element 10 is disposable between a plug 1 (see Figure 2A and Figure 2B) and a socket (not shown), the safety element 10 comprising a thermal expansion member (not shown); wherein the safety element 10 is configurable in: a first configuration, wherein the safety element 10 is disposed between the plug 1 and the socket and wherein the safety element 10 has a first thickness, whereby the plug 1 and the socket are mutually electrically coupled; and a second configuration, wherein the safety element 10 is disposed between the plug 1 and the socket and wherein the safety element 10 has a second thickness greater than the first thickness, whereby the plug 1 and the socket are mutually electrically uncoupled; wherein the safety element 10 is configured to move from the first configuration to the second configuration upon heating of the thermal expansion member to or above a threshold temperature.

In this example, the plug 1 and the socket are an AC power plug and an AC power socket, respectively, particularly Type G.

In this example, the safety element 10 has a first face 11 and a second face 12, wherein the first face 11 and the second face 12 are mutually opposed, wherein the first face 11 is arranged to contact or confront the plug 1 , for example a base thereof, and wherein the second face 12 is arranged to contact or confront the socket, for example a faceplate thereof, or vice versa. In this example, the safety element 10 comprises a housing 100 having a first wall 101 and a second wall 102, wherein the first wall 101 and the second wall 102 are mutually opposed, and wherein the thermal expansion member is arranged (i.e. located, positioned) between, for example wholly between, the first wall and the second wall, for example as a first layer (i.e. the first wall), as a third layer (i.e. the thermal expansion member) and as second layer (i.e. the second wall), respectively. In this example, the first face 11 is provided by the first wall 101 and the second face 12 is provided by the second wall 102. In this example, the housing 100 has a side wall 103 between the first wall 101 and the second wall 102, wherein the thermal expansion member is enclosed (hermetically sealed) within, for example wholly within, the housing. In this example, the housing is an expandable housing having an extensible or deformable side wall, such as a resilient side wall. In this example, the housing 100 comprises a polymeric composition comprising a polymer, particularly a thermoplastic polymer.

In this example, the safety element 10 is in the form of a sheet.

In this example, a perimeter P of the safety element 10 conforms with a perimeter p of the plug 1 , for example wherein the perimeter P of the safety element 10 is within the perimeter p of the plug 1. In this example, a shape of the safety element 10 is similar to a shape of the plug 1 , particularly triangular.

In this preferred example, the safety element 10 has a shape and dimensions, including the first thickness, similar to or the same as a wiring safety diagram card, such as included on a new plug 1 .

In this example, the thermal expansion member is a hard char intumescent, enclosed in the expandable housing of the safety element.

In this example, the first thickness T1 is in a range from 500 pm to 1 mm.

In this example, the second thickness T2 is in a range from 4 mm to 10 mm.

In this example, the safety element 10 is configured to remain in the second configuration upon cooling of the thermal expansion member below the threshold temperature.

In this example, the safety element 10 is configured to irreversibly move from the first configuration to the second configuration upon heating of the thermal expansion member to or above a threshold temperature.

In this example, the threshold temperature is in a range from 50 °C to 200 °C. In this example, a difference between the first thickness T1 and the second thickness T2 is in a range from 2 mm to 10 mm.

In this example, a ratio of the second thickness T2 to the first thickness T1 is in a range from 3 : 1 to 50 : 1 .

In this example, a force exerted by the safety element 10 on the plug 1 and/or the socket upon moving from the first configuration to the second configuration is in a range from 5 N to 50 N.

In this example, a pressure exerted by the safety element 10 on the plug 1 and/or the socket upon moving from the first configuration to the second configuration is in a range from 5 kPa to 100 kPa.

In this example, the safety element 10 is configured to move uniaxially from the first configuration to the second configuration upon heating of the thermal expansion member to or above a threshold temperature.

In this example, the safety element 10 comprises a set of perforations 1000, including a first perforation 1000A, therethrough correlating (i.e. aligned) with a set of pins of the plug. In this example, the set of perforations 1000 includes the first perforation 1000A, a second perforation 1000B and a third perforation 1000C, for a three pin plug. In this example, the first perforation 1000A, the second perforation 1000B and the third perforation 1000C are rectangular, having a clearance fit with respect to the set of pins of the plug.

Figure 2A is a CAD perspective view of the safety element 10 of Figure 1 provided on a plug 1 , wherein the safety element 10 is configured in a first configuration; and Figure 2B is a CAD perspective view of the safety element of Figure 1 provided on the plug 1 , wherein the safety element 10 is configured in a second configuration.

The safety element 10 has the first thickness T 1 in the first configuration.

The safety element 10 has the second thickness T2 in the second configuration.

Figure 3 schematically depicts AC power plugs and sockets for exemplary embodiments.

Figure 4 schematically depicts a method according to an exemplary embodiment. The method is of mutually electrically uncoupling a plug and a socket upon heating to or above a threshold temperature.

At S401 , the method comprises configuring a safety element, comprising a thermal expansion member, in a first configuration, wherein the safety element is disposed between the plug and the socket and wherein the safety element has a first thickness, whereby the plug and the socket are mutually electrically coupled.

At S402, the method comprises moving the safety element from the first configuration to a second configuration by heating the thermal expansion member to or above the threshold temperature, wherein the safety element is disposed between the plug and the socket and wherein the safety element has a second thickness greater than the first thickness, whereby the plug and the socket are mutually electrically uncoupled.

Although a preferred embodiment has been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims and as described above.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.