AU2012100414A4 - Electrical plug - Google Patents

Abstract

Abstract An electrical plug comprising at least two plug terminals; an overload device operative to change from a closed condition to an open condition when a threshold temperature is reached within the device; and a temperature 5 regulating arrangement operative to maintain different temperature zones within the plug such that when the threshold temperature is reached in the overload device, the plug terminals are maintained at a temperature below said threshold. 3038623_1 (GHMatters) P86157.AU rn w rrz 4

Description

AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION Innovation Patent Applicant (s): Legrand Australia Pty Ltd Invention Title: ELECTRICAL PLUG The following statement is a full description of this invention, including the best method for performing it known to me/us: - 2 ELECTRICAL PLUG Technical field 5 The present disclosure relates to an electrical plug and more specifically to an electrical plug that incorporates an overload device. Background of the Invention 10 Electrical devices, such as power boards, often include an associated overload device to protect the electrical device, any appliance connected to the device, and the power socket from electrical or thermal overload. Typically these overload devices are included in electrical device body. The overload device is typically arranged to break an electrical connection within the circuit to stop the is flow of current if the device heats up beyond a threshold temperature. In some circumstances it is desirable if the overload device is fitted within the plug of the electrical device rather than in the device housing. Such an arrangement is problematic in maintaining correct calibration of the overload 20 device without overheating the plug particularly where it is also desired to maintain a compact design for the plug. Summary 25 In one embodiment an electrical plug comprises: at least two plug terminals, an overload device operative to change from a closed condition to an open condition when a threshold temperature is reached within the device, and a temperature regulating arrangement operative to maintain different temperature zones within the plug such that when the threshold temperature is 30 reached in the overload device, the plug terminals are maintained at a temperature below said threshold. 3038623 1 (GHMatters) P86157.AU -3 In a further form the temperature regulating arrangement is operative to maintain heat in the overload device in a heat generation region of the overload device so as to maintain correct calibration of the overload device, and to dissipate heat more readily in the region of the plug terminals. 5 Brief Description of the Drawings Fig. 1 shows a perspective view of a plug; Fig. 2 shows another perspective view of the plug of Fig. 1; 10 Fig. 3 shows an exploded view of the plug with its various components; Fig. 4 shows a schematic diagram of the plug and the various wires in the plug; Fig. 5 shows a view of the overload device and the internal details of the overload device; and 15 Fig. 6 shows a cross sectional view of the plug. Detailed Description of Embodiments of the Invention In the following detailed description, reference is made to the accompanying 20 drawings which form part of the detailed description. The illustrated embodiments described in the detailed description and depicted the drawings, are not intended to be limiting. Other embodiments may be utilised and other changes may be made within departing from the spirit or scope of the subject matter presented. It will be readily understood that the aspects of the present 25 disclosure are generally described herein and illustration of the drawings can be arranged, substituted, combined, separated and designed in a wide variety of different configurations, all of which are contemplated in this disclosure. This disclosure is directed to an electrical plug including an overload device, in 30 particular a thermal overload device. A thermal overload device is arranged to trip and break an electrical connection when the temperature in the overload device exceeds a threshold temperature. 3038623 1 (GHMattersl P86157.AU -4 The overload device is arranged to use current flowing through it to heat up and open a contact in the device at a predetermined threshold temperature. Whilst it is desirable in some instances to include an overload device within the 5 plug (rather than say in the housing of an electrical appliance) such an arrangement has the potential to overheat the plug. There are often strict controls established (such as in the Australian Standards) to regulate the temperature of the plug in operation. Excessive heating of a plug may cause damage to the terminals and may lead to other hazards such as an electrical 10 fire. Disclosed in some embodiments is an electrical plug comprising at least two plug terminals, an overload device operative to change from a closed condition to an open condition when a threshold temperature is reached within the device is and a temperature regulating arrangement operative to maintain different temperature zones within the plug such that when the threshold temperature is reached in the overload device, the plug terminals are maintained at a temperature below the threshold. 20 In one form the temperature regulating arrangement is operative to maintain heat in the overload device in a heat generation region of the overload device so as to maintain correct calibration of the overload device, and to dissipate heat more readily in the region of the plug terminals. 25 In one form the temperature regulating arrangement comprises first and second insulation components, the first insulation component being disposed at a region of the overload device and the second insulation component being disposed at or adjacent the plug terminals, the first insulation component having higher insulation properties than the second insulation component. 30 In one embodiment the overload device has opposite first and second sides, wherein the first side faces away from the plug terminals and the second side faces towards the plug terminals, and wherein the first insulation component is 30386231 (GHMatters) P86157.AU - 5 disposed on or adjacent the fist side and the second insulation component is disposed intermediate the second side of the overload device and the plug terminals. 5 In one form the overload device includes first and second connection terminals, and the wherein in operation of the overload device the first connection terminal tends to heat up greater than the second connection terminal, and wherein the temperature regulating arrangement comprises a wiring configuration in the form of an input cable connecting one of the plug terminals and the second 10 connection terminal of the device and an output wire connected to and extending from the first terminal. In a further form the overload device further comprises a heating element that interconnects the first and second connection terminals when the overload 15 device is in the closed condition, the heating device being operative to move out of contact with the second terminal when the heating element reaches the threshold temperature. In one embodiment the input cable is a higher insulated rated wire than the 20 output wire. An aim of the temperature regulating arrangement is to contain the heat generated at the overload device within the overload device and allow higher heat dissipation in the vicinity of the plug terminals and other parts of the plug in 25 order to keep the plug terminals from overheating. The temperature regulating arrangement is advantageous as it is operative to maintain different temperature zones within the plug such that when the threshold temperature is reached in the overload device, the plug terminals are maintained at a temperature below the threshold. Further whilst the plug terminals are protected 30 from excessive temperature increase, the heat is localised in the overload device thereby allowing for the correct calibration of the overload device to be maintained. 3038623 1 (GHMattersi P86157.AU - 6 An embodiment of an electrical plug will be described with reference to the appended figures. Figs. 1 and 2 show an embodiment of an electrical plug 1. The plug comprises a housing 2 including a first opening 3 and a second opening 4 positioned at opposite ends of the housing 2. The housing 2 may be s formed from a plastics material by any suitable process such as vacuum forming or moulding. In one form the housing 2 may be formed from interfitting two parts (2a and 2b), as illustrated in Fig. 3. The first housing part 2a may be fastened to the second 10 housing part 2b by screws 5 or any other fastener such as a bolt, nail, rivet. In an alternate form the two parts 2a, 2b of the housing may be glued or welded together. In one embodiment the plug comprises three plug terminals 6a, 6b, 6c, as 15 illustrated in Figs. 1, 2 and 3. In an alternate embodiment the plug may comprise only two plug terminals. In the illustrated embodiment the plug 1 comprises an active plug terminal 6a, a neutral plug terminal 6b and an earth plug terminal 6c. The plug terminals 6a, 6b, 6c extend out of the housing 2 through openings 10a, 10b and 10c. 20 The plug further comprises an external supply cord 7 that in the illustrated form, extends out of opening 3. The cord 7 is used to supply electricity to an electrical device such as a power board or an appliance or another suitable electrical device associated with the plug. The cord 7 comprises a plurality of 25 output wires 7a, 7b, 7c which connect with a respective one of plug terminal 6a, 6b, 6c and are covered by insulation to form the cord 7. The plug 1 also includes an overload device 20 mounted within the housing 2. In the illustrative form, the overload device 20 connects between the plug active 30 terminal (i.e. active pin) 6a and the output wire 7a that corresponds with the plug active terminal 6a. The overload device 20 will be described in more detail with respect to Figs. 5 and 6. AARA7l 1 ICHMa"ttari PAAi 17 Al I The overload device 20 is arranged to break the connection between the active terminal 6a and the output wire 7a, in order to break the electrical circuit and stop the current flow. The overload device 20 is arranged to break the connection (trip) when a heating device within the overload device reaches a 5 threshold temperature typically due to excessive current in the circuit. The overload device 20 acts as a safety device that breaks the circuit within the plug to isolate the plug in case of overloading of the circuit or from a short circuit of the appliance. 10 Fig. 5 shows a detailed view of an illustrative form of the overload device 20. The overload device 20 comprises a first connection terminal 22 that is connected to the active output wire 7a, a second connection terminal 23 that is connected to the active plug terminal 6a through an input wire 40 (as described in more detail below) and a heating element 24 interconnecting the two is terminals. The terminals 22, 23 and the heating element 24 are housed within the device casing 21. The heating element 24 completes the circuit between the first and second connection terminals 22, 23 and allows current to flow from the active plug terminal 6a to the active output wire 7a. 20 In the illustrated form, the heating element 24 is permanently connected to the first connection terminal 22 and engages and disengages with the other terminal 23 depending on the state of the overload device. The heating element 24 is arranged to flex or deform when heated under current flow across the element and is moveable between an open and a closed position. In the 25 closed position the heating element 24 interconnects the two terminals 22, 23 thereby maintaining the electrical circuit. In the open position the heating element 24 maintains connection with the first terminal 22 but is disconnected from the second terminal 23 thereby breaking the electrical circuit. Fig. 5 shows the heating element 24 in an open position where it is disconnected from the 30 second connection terminal. In one form the heating element 24 is made of a bimetal material. Any two suitable metals can be used together to form a bimetal material. Some 30I3873 1 (HMattar PRA157 All - 8 examples of suitable metals are steel, zinc, copper or aluminium. In another form the heating element 24 may be formed from a metal alloy. In a further form the heating element 24 may be formed from a single metal. In yet another embodiment the heating element 24 may be formed from any combination of 5 bimetal, alloy and metals. The heating element 24 must be formed from a material that can conduct electricity. The heating element 24 is operative to move to the open position when the heating element reaches a threshold temperature. In operation the heating 10 element is arranged to flex when the temperature of the heating element 24 exceeds a predetermined threshold temperature, thereby allowing for a sudden break (trip) in the circuit as the device moves to the opened position. In the illustrated form, the overload device 20 may comprise a reset mechanism is 15 as shown in Fig. 3 that is accessible through the opening 4. The reset mechanism 15 may comprise a button or an opening for a tool that can be used to reset the overload device. In another embodiment the overload device may reset itself once the temperature in the overload device or in the plug drops to a designated level. 20 In operation of the overload device, there is a large amount of heat generated in the overload device since the overload device is arranged to heat up and trip when the temperature reaches the threshold temperature. The heat generated in the overload device is required to be contained and not transfer to the plug 25 terminals or this can lead to damage of the plug terminals. In the illustrated form, the plug 1 comprises a temperature regulating arrangement 30 that is operative to maintain different temperature zones within the plug such that when the threshold temperature is reached in the overload 30 device 20, the plug terminals 6a-6c are maintained at a temperature below the threshold temperature and at a safe operating temperature. The temperature regulating arrangement 30 may comprise a variety of forms or combinations with the plug to achieve this outcome. 3038623 1 (GHMattersl P86157.AU A further feature of the temperature regulating arrangement 30 is to maintain sufficient heat in the overload device 20 in a heat generation region of the overload device 20 so as to maintain correct calibration of the overload device, whilst allowing heat to dissipate more readily in a region of the plug terminals s 6a-6c. In one form, as illustrated in Fig. 6 the temperature regulating arrangement 30 comprises at least a first insulation component 31 and a second insulation component 32. 10 As seen in Fig. 6, the overload device 20 comprises a first side 25 and second side 26, wherein the first side 25 faces away from the plug terminals 6a-6c and the second side 26 faces towards the plug terminals 6a-6c. As shown, the first insulation component 31 is disposed on or adjacent the first side 25 of the 15 overload device 20. The second insulation component 32 is disposed on or adjacent intermediate the second side 26 of the overload device 20 and the plug terminals 6a-6c, as shown in Fig. 6. The first and second insulation components may be made from any suitable 20 thermally insulative material such as a plastics material or rubber or any other thermally insulative material. The first and second insulation component may also be electrically insulative material that does not allow current to flow through them. 2S In the form as shown, the second insulation component 32 has less insulation properties than the first insulation component 31. This arrangement is designed to create a micro-ambient environment around the overload device 20 that allows the overload device to maintain correct calibration whilst allowing heat to dissipate from the plug terminals. In particular the first insulation component 30 31 is in facing engagement with overload device but remote from the plug terminals. This allows heat to be captured in an area remote from the plug terminals thereby allowing a micro environment that will allow adequate heat to be retained to maintain calibration of the overload device. The second qn~l 1 fI 0U-. 1 C~7 ...

- 10 insulation component 31 has less insulative properties and therefore allows heat to dissipate from the plug more readily, thereby maintaining the plug terminals at a lower temperature. 5 The insulation components 31, 32 may be shaped with fins 33 to form air pockets 34 disposed between the first and second insulation components and the overload device to provide additional thermal insulation of the overload device 20. 10 The temperature regulating arrangement 30 also comprises a wiring configuration in the form of a high insulation input cable 40 that extends between the connection terminal 23 and plug terminal 6a to further thermally insulate and isolate the plug terminal from the overload device 20. The high insulation input cable is arranged to further reduce heat transfer from the 15 overload device to the plug terminal thus ensuring the temperature of the plug terminals does not increase above the allowable limit. The connection terminals 22, 23 are formed from any suitable conductive material. In operation of the overload device 20, the first connection terminal 20 22, to which the heating element 24 is permanently attached gets hotter than the second connection terminal 23. By connecting the plug terminal to the second connection terminal 23 rather than the first connection terminal 22, and using a higher rated input cable 40, it is possible to further reduce the heating of the plug terminals. 25 In operation, current flows from the active plug terminal 6a, through the input cable 40, through the second connection terminal, into the heating element 24, and to the output wire 7a via the first connection terminal 22. The input cable 40 is a higher insulated rated wire than the output wire 7a. The higher insulated 30 rated input cable 40 reduces the heat transfer to the plug terminals. This wiring configuration, in combination with the insulating arrangement in the plug with the first and second insulation components 31, 32, allows the temperature regulating arrangement 30 is able to maintain sufficient heat in the overload 3038623_1 (GHMatters) P86157.AU - 11 device 20 in a heat generation region of the overload device 20 so as to maintain correct calibration of the overload device, whilst simultaneously maintaining the temperature of the terminals at an acceptable operating level. 5 It will be understood to persons skilled in the art of the invention that many modifications may be made without departing from the spirit and scope of the invention. It is to be understood that, if any prior art publication is referred to herein, such 10 reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country. In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or 15 necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. 20 3038623 1 (GHMattrni PRA157 AUl

Claims (8)

1. An electrical plug comprising: at least two plug terminals; 5 an overload device operative to change from a closed condition to an open condition when a threshold temperature is reached within the device; and a temperature regulating arrangement operative to maintain different temperature zones within the plug such that when the threshold temperature is 10 reached in the overload device, the plug terminals are maintained at a temperature below said threshold.

2. An electrical plug according to claim 1, wherein the temperature regulating arrangement is operative to maintain heat in the overload device in a 15 heat generation region of the overload device so as to maintain correct calibration of the overload device, and to dissipate heat more readily in the region of the plug terminals.

3. An electrical plug in according to claim 1 or 2, wherein the temperature 20 regulating arrangement comprises first and second insulation components, the first insulation component being disposed at a region of the overload device and the second insulation component being disposed at or adjacent the plug terminals, the second insulation component having higher insulation properties than the first insulation component. 25

4. An electrical plug according to claim 3 wherein the overload device has opposite first and second sides, wherein the first side faces away from the plug terminals and the second side faces towards the plug terminals, and wherein the first insulation component is disposed on or adjacent the first side and the 30 second insulation component is disposed intermediate the second side of the overload device and the plug terminals. 3D3RA3 I IHMntfirul PRR17 All - 13

5. An electrical plug according to any preceding claim wherein the overload device includes first and second connection terminals, and the wherein in operation of the overload device the first connection terminal is hotter than the second connection terminal, and wherein the temperature 5 regulating arrangement comprises connecting an input cable between one of the plug terminals and the second connection terminal of the device and an output wire to the first terminal.

6. An electrical plug according to claim 5, wherein the overload device 10 further comprises a heating element interconnecting the first and second connection terminals when the overload device is in the closed condition, the heating device being operative to move out of contact with the second terminal when the heating element reaches the threshold temperature. is

7. An electrical plug according to claim 5 or 6, wherein the input cable is a higher insulated rated wire than the output wire.

8. An electrical plug substantially as herein described with reference to the accompanying drawings 3038623_1 (GHMatters) P86157.AU