AU2007100860A4 - An Electrical Socket - Google Patents

Description

Regulation 3.2

AUSTRALIA

PATENTS ACT, 1990 COMPLETE SPECIFICATION FOR AN INNOVATION PATENT

ORIGINAL

Name of Applicant: Actual Inventors: Address for servce in 1\ LSrtralIia: Inlvefition Title: SCH-NIL-1IILR ElL:-,C'iRIC NE\V ZALAN 1-101DiINGS II i IF) .JOH-N G I1LS, a citizen of the United K ingdomn and New Zealand of 323 Coldstrcam- Road, Rangiora, North Canterburv, New Zealand and RA\JINL)K--R SING H, a Newv Zealand citizen of 55 Westgrove Avenue, A;vonhecad, Christchurch, New Zealand I PAR,cvl 11, 60 Marcus Clarke Street, Canberra A 2601, Australia A \N ELCRCLSOCK i-, T[he following statemencit is a full description of thlis invention, Including the becst method of performing it known to uts.

FIELD OF INVENTION

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The invention relates to improvements in electrical socket fittings of the type adapted to be fitted over an aperture in the lining of a wall in a domestic or light commercial or industrial application (sometimes referred to as hot points), which will herein be referred to as wall socket fittings for convenience.

\0 BACKGROUND

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0 Single or double electrical socket fittings for use in providing power outlets in domestic or light commercial or industrial applications comprise a body or plate-like part which when the fitting is O installed typically fits over an aperture in the lining of a wall of a house or office or similar. The C1 installed fitting then provides an exposed front face which presents phase, neutral, and earth socket apertures in a standard format, into which the plug connector of any appliance may be inserted. The metallic pins of the plug insert through the socket apertures and make contact with metallic connector parts of the outlets behind the front face of the fitting, when a plug is plugged into the socket. Such socket fittings also have terminators at the rear of the fitting which are exposed into the wall cavity and to which fixed wiring is terminated to connect power to the socket. Commonly such fittings also have mounting apertures through which screws pass, into a box fixed for example to a structural member within the wall cavity, to fix the fitting in place.

Such socket fittings may also comprise a cover plate which is installed to finish the front face of the fitting, or alternatively the main fitting part which is screwed to the wall may form the finished front face of the fitting, with plugs optionally being provided over the mounting apertures for use after fixing the fitting in place.

SUMMARY OF INVENTION It is an object of the invention to provide an improved or at least alternative form of such a wall socket fitting.

In broad terms the invention comprises an electrical wall socket fitting adapted to be fitted over an aperture in the lining of a wall and comprising a front face which presents at least one outlet of phase, neutral, and earth apertures in a standard format, terminators exposed at a rear of the fitting for connecting thereto fixed mains wiring within the wall cavity, internal switching means, and a thermal sensor arranged to trigger the internal switching means to operate to disconnect power flow through the outlet on sensing a temperature increase above a temperature threshold, due to high current flow through the socket fitting.

O The thermal sensor may comprise a thermistor or other heat sensitive electrical device. The C, sensor may be positioned in close physical proximity to or fixed to a metal part of the fitting behind the q) front face, through which current flows when an appliance is connected to the outlet. Preferably the thermal sensor is in a position effective to sense heat generated due to a poor (high resistance) connection between a plug pin or pins and a receiving connector or connectors of the socket.

Whether or not the socket is a switched or non-switched fitting, the fitting also comprises a \Q separate internal switching means such as a small electrical switch mechanism behind the front face of 00 Sthe fitting, through which power to the socket outlet(s) passes, and an electronic control circuit to which the thermal sensor is connected. The control circuit is arranged to trip the switch mechanism 0 when an over temperature condition is detected, to then disconnect mains power to the outlet(s). The C1 electronic control circuit may also comprise means to sense the voltage difference between the phase and neutral and if the difference is detected to be less than (voltage sag) or greater than (voltage surge) a predetermined voltage threshold in either case, to disconnect mains power to the outlet(s). Such voltage can sags or surges damage appliances. The switching means may comprise an associated solenoid, and have contacts which are latched closed in normal powerflow and now power conditions, and which are opened when the solenoid is de-energised by the control circuit, when the control circuit is triggered by an over temperature, voltage, sag, or voltage surge condition.

The electrical fitting preferably also comprises a I.ED or neon or other visible indicator, visible from the front face of the fitting, which in one form may indicate when the socket outlet is live and in another form may indicate when an over temperature or voltage sag or surge condition has been sensed and power flow through the socket has been automatically disconnected. In another form the LED or neon or other visible indicator may flash periodically on and off when the temperature is above a predetermined threshold, or voltage is below or above predetermined thresholds, nearing the cut-off threshold in each case.

The electrical socket may also comprise a small reset switch or other mechanical or contact switch or pressure pad also exposed at the front face of the fitting, which may be manually operated to re-energise the socket, once the cause of an over temperature condition has been removed, or after a voltage sag or surge condition.

Electrical socket fittings of the invention provide integral protection against over temperature conditions caused by powering an excessive number of appliances through the one socket for example, or by a fault in the socket itself such as a poor connection between a socket connector and a pin of a plug inserted into the socket (the likelihood of which may in turn be increased by high current flow because an excessive number of appliances is being powered through the socket).

S' The term "comprising" as used in this specification means "consisting at least in part of".

1 When interpreting each statement in this specification that includes the term "comprising", features other than that or those prefaced by the term may also be present. Related terms such as "comprise" and "comprises" are to be interpreted in the same manner.

BRIEF DESCRIPTION OF THE FIGURES \0 A preferred embodiment of the invention is described with reference to the accompanying 00 0 drawings, by way of example in which:Figure 1 is a view of the preferred form socket fitting from the front (showing the front face thereof), O Figure 2 is a view from the front, of the preferred form socket fitting with a front part removed so that N the internal components of the fitting are visible, and Figure 3 is a view similar to Figure 2 but with the metallic socket connector pins and other metallic parts of the preferred form socket also removed.

DETAILED DESCRIPTION OF PREFERRED FORM Referring first to Figure 1, the preferred form socket fitting comprises a body part 1 having a front face which is exposed and presents two outlets each comprising phase, neutral, and earth socket apertures in a standard format, when the fitting is connected and installed in place over an aperture in the lining of a wall. In the particular embodiment shown the socket fitting is a switched double outlet fitting but alternatively the socket fitting may be a switched or unswitched single or triple or quad socket fitting. The front face of the fitting shown in Figure 1 may comprise a cover plate over a main body part of the fitting which is fixed over the wall aperture, or alternatively the front face of the main body part may be the finished front face of the fitting (without any separate cover plate).

An LE) 2 is exposed through an aperture in the front face of the fitting, which is normally illuminated, and is not illuminated in the event of an over temperature (or voltage sag or surge) condition as will be further described, to indicate to persons that the integral over temperature protection has operated to disconnect power from the outlets. Alternatively the LED may be illuminated only when power is disconnected from the outlets, in the event of an over temperature (or voltage sag or surge) condition. The preferred form fitting also comprises a small reset buttonoperated switch 3 exposed through the front face of the fitting, which a person may push to re-energise the outlets, after for example disconnecting excess appliances (or after a voltage sag or surge condition).

Alternativelv this switch may be actuated by a contact or pressure pad at the front face of the fitting.

O Referring to Figures 2 and 3, which show the fitting of Figure 1 behind the front face thereof, CN each outlet behind the front face comprises metallic phase, neutral and earth connectors 4, 5 and 6, into which the pins of a plug inserted into the socket engage. The connectors 4, 5 and 6 on either side ND comprise integral parts which connect to a switch mechanism on either side partly and generally O indicated at 7 in Figure 2, which may otherwise be of conventional form. The fitting also comprises terminators 8 exposed at the rear of the fitting and which in the preferred form are screw terminators, \0 which when the wall fitting has been installed are exposed at the rear of the fitting for connecting mains 00 O wiring within the wall cavity to the fitting (the wire ends are connected to the screw terminators 8

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S before the electrical fitting is in turn screwed to the wall). The terminators 8 may be of conventional O form.

C In accordance with the invention the fitting comprises a small electrical switch mechanism which may be of any form, and which is in the preferred form housed within a casing 12, and through which the phase line is connected from the phase terminator 8 at the rear of the fitting, to the phase outlet connectors 4. Preferably the switch mechanism 9 switches both the phase and neutral lines between the phase and neutral terminators 8 and the phase and neutral socket connectors 4 and 5. In a preferred form the switch mechanism 9 comprises mechanical contacts (not shown) which under normal (no fault) and no power conditions are latched closed and in an over temperature (fault) condition are opened by a small solenoid actuator (not shown). In turn a control circuit provides power to this solenoid, and is connected to thermistors 10, so that if over temperature condition at either outlet is sensed, then the solenoid is energised by the control circuit causing the switch mechanism 9 to open to disconnect power to all socket connector pins (at least the phase connectors 4 and preferably both the phase connectors 4 and neutral connectors A separate thermistor 10 is positioned in close physical proximity to or in contact with a metal part which is integral with one of the phase connectors 4 of each outlet (see in particular Figure 3).

The arrangement is such that an over temperature condition within the socket fitting for example from a poor connection between the phase pin of a plug and a phase connector 4 causing heat build up, will trigger the control circuit and cause release of the switch mechanism 9 to disconnect power from the outlets of the fitting.

In a preferred form, the control circuit comprises a microprocessor or microcontroller or other analogue or digital hardware. Optionally, control software is provided. The control circuit is arranged to receive the output signals from the thermal sensors. In the preferred form the control circuit is also arranged to sense or measure the difference in voltage between the phase and neutral connections.

With the temperature and voltage information, the control circuit uses an algorithm executed in Shardware or software or both to determine when the temperature exceeds a predetermined temperature CN threshold, or if the voltage sags or surges below predetermined voltage thresholds. In any such condition the control circuit energises the solenoid to open the internal switch mechanism 9, and also de-illuminates the visible indicator 2. Additionally, the control circuit may be arranged so that if the temperature is within a predetermined range from the cut-out point, or if there is voltage sag or surge approaching a limit, so that cut-out is imminent, the control circuit actuates the visible indicator 2 to 00 O flash periodically on and off. This warns users that the socket is near tripping point.

0 When the control circuit causes the switch mechanism 9 to disconnect power from the outlets of the fitting, subsequently a person may reset the fitting by pressing the reset switch 3, which will re- O latch the switch mechanism 9 closed to re-energise the outlets of the socket fitting, provided that the CN condition which led to initial triggering has been removed.

The foregoing describes the invention including a preferred form thereof. Alterations and modifications as would be obvious to those skilled in the art are intended to be incorporated within the scope hereof, as defined in the accompanying claims.

Claims (4)

1. An electric wall socket fitting adapted to be fitted over an aperture in the lining of a wall, and Scomprising; O a front face which presents at least one outlet of phase, neutral, and earth apertures; phase, neutral, and earth connectors accessible through said phase, neutral and earth apertures \O in the front face; 00 O phase, neutral, and earth terminators exposed at a rear of the fitting; a thermal sensor sensitive to temperature change due to the current flow through the outlet; l"- O and CK1 internal over temperature switching means arranged to interrupt the power flow in the event of a sensed temperature increase above a predetermined threshold due to high current flow.

2. An electric wall socket fitting according to claim 1 wherein the thermal sensor comprises a thermistor.

3. An electric wall socket fitting according to either of claims 1 or 2 wherein the internal switching means comprises a switch mechanism and an associated solenoid.

4. An electric wall socket fitting according to any one of claims 1 to 3 comprising an indicator visible from the front face of the fitting, the visible indicator arranged to indicate the status of the electric wall socket fitting. An electric wall socket fitting according to any one of claims 1 to 4 comprising a user operable switch for resetting the internal switching means after the cause of an over temperature condition has been removed.