Field of invention

[01] This invention relates to a mains power socket having an extensible and retractable lead.

Background to the invention

[02] A significant hazard exists in the form of extension leads that are plugged into wall sockets for electrical power. Often the user may not notice defects with the extension lead and with the plug at the wall end of the lead and the socket body at the remote end into which a distal appliance is to be connected. The defects may simply be the result of lengthy use developing wear and tear. The result often goes unnoticed by the user, especially a user who may lack knowledge and appreciation of the dangers associated with electrical energy supply.

[03] Such a user may also not appreciate the risks associated with using a long extension lead that is wound up in a coil when not in use and with which only a short distance needs to be bridged. The user may find each end of the lead, connect to the wall socket and plug in the appliance to be used, without unwinding the main coil of the lead. This practice may lead to overheating within the coil causing elevated fire risk, the generation of induced currents and the creation of magnetic fields that can disrupt operation of other equipment in the vicinity.

Objects of the invention

[04] It is an object of this invention to address the shortcomings of the prior art and, in doing so, to provide a power supply installation having a stored and automatically retractable extension cord.

[05] The preceding discussion of the background to the invention is intended to facilitate an understanding of the present invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge in Australia or elsewhere as at the priority date of the present application.

[06] Further, and unless the context clearly requires otherwise, throughout the description and the claims, the words ‘comprise’, ‘comprising’, and the like are to be construed in the inclusive sense of “including, but not being limited to” - as opposed to an exclusive or exhaustive sense meaning “including this and nothing else”.

Summary of invention

[07] According to a first aspect of the invention there is provided an electrical power outlet installation comprising: a. a bracket mountable to wall structure, b. a winder mechanism mounted to the bracket, the winder mechanism comprising an elongate cylinder rotatable supported on an axle; c. an electrical cord windable around the cylinder, a first end of the cord being operatively connected to a power source terminal and a second end of the cord being conductively connected to a power socket arranged to be gripped by hand and withdrawn from the bracket, whereby withdrawal of the power socket causes the cord to be unwound, d. the winder mechanism comprising biasing means applied to the cylinder to cause the cylinder to rotate in a direction for retracting an unwound length of the cord, and e. releasable arresting means operable to interact with the cylinder for preventing retraction of the unwound length.

[08] In a preferred form of the invention, the winder mechanism is operatively configured for preventing winding of the cord over itself when retracted.

[09] Preferably, the cylinder has a surface comprising a helical groove into which the cord is wound by rotation of the cylinder. [010] In an embodiment, the installation further comprises a winding guide mounted within the bracket to extend substantially the length of the cylinder, the guide being spaced from the surface at a distance therefrom which is less than the diameter of the cord.

[011] In a further preferred form of the invention, the biasing means comprises pre-stressed spring means.

[012] In a still further preferred form of the invention, the releasable arresting means comprises a frictional braking mechanism operatively connected with the cylinder. In an embodiment, the mechanism comprises a ratchet and pawl.

[013] Preferably, the installation comprises hand-actuable means for releasing the pawl temporarily for allowing rewinding of the cord. The release means preferably comprises a push-button. The button is preferably accessible through a cover plate of the installation.

[014] In a yet further preferred form of the invention, the installation includes isolating means operable to prevent electrical current reaching the socket unless the cord has been fully withdrawn.

[015] Preferably, the isolating means comprises a snap action switch (also known as a micro-switch) that interacts with the cord. The micro-switch may be located between an end of the cord and a mains power terminal. In a different embodiment, the isolating means comprises a proximity switch.

[016] The cylinder is preferably horizontally disposed within the bracket.

[017] According to a second aspect of the invention, there is provided a method of extending an electrical lead comprising steps of: a. providing an installation adapted for mounting to a wall by means of a mounting bracket, the installation comprising a power cord wound up on a winder cylinder rotatably supported by the bracket; an end of the cord being operatively connected to a power socket-containing body; b. withdrawing the body from a first position on the installation and displacing it to a second location remote from the installation at which it is desired to supply electrical power, withdrawal and displacement of the body causing the cord to be unrolled from the winder cylinder; c. providing an arresting mechanism in the installation operatively mounted to prevent retraction of the cord unless the mechanism is released; d. operatively connecting the installation to a power supply available at the wall, whereby electrical power is able to be supplied to the socket body.

[018] In a preferred form of the invention, the method includes preventing winding of the cord over itself when retracted.

[019] The arresting mechanism may include a friction braking mechanism or a ratchet and pawl mechanism.

[020] The method preferably includes providing the cylinder with a surface comprising a helical groove into which the cord is wound by rotation of the cylinder.

[021] The method preferably further includes providing guide means and operatively mounting the guide means within the bracket to extend along the cylinder and leave insufficient gap between the guide means and the cylinder surface for a second cord section to be wound over a first cord section located between the second cord section and the power supply.

[022] In a preferred embodiment, the invention includes providing biasing means in the installation, the biasing means operable to cause automatic retraction of the cord when the arresting mechanism is released.

[023] In an embodiment, the biasing means comprises tensioned spring means.

[024] In a further preferred form of the invention, the method includes the step of operating hand-actuable means for releasing the arresting mechanism temporarily for allowing rewinding of the cord. [025] In a still further preferred form of the invention, the method includes the step of operating electrical isolation means to isolate the cord from the power supply unless the cord has been wound out fully.

[026] In an embodiment, the isolation means comprises a snap action or micro-switch. In another embodiment, the isolation means comprises a proximity switch.

[027] According to a third aspect of the invention there is provided a power point installation in kit form, the kit comprising: a. a bracket mountable to wall structure, b. a winder mechanism for mounting to the bracket, the winder mechanism comprising an elongate cylinder rotatably supportable on an axle; c. an electrical cord windable around the cylinder, a first end of the cord being operatively connected to a power-receiving terminal and a second end of the cord being conductively connectable to a power socket arranged to be gripped by hand and withdrawn from the bracket, whereby withdrawal of the power socket causes the cord to be unwound from the cylinder, d. the winder mechanism comprising biasing means applied to the cylinder to cause the cylinder to rotate in a direction for retracting an unwound length of the cord, and e. releasable arresting means operable to interact with the cylinder to prevent retraction of the unwound length.

[028] In the kit, the winder mechanism preferably includes means operatively configured for preventing winding of the cord over itself when retracted.

[029] In a preferred form of the invention, the cylinder in the kit has a surface comprising a helical groove into which the cord is wound by rotation of the cylinder. [030] In a preferred embodiment, the kit comprises a thermally sensitive switch automatically disrupting power supply to the socket body when a threshold temperature is reached in the installation.

Brief description of drawings

[031] In order that the invention may be readily understood, and put into practical effect, reference will now be made to the accompanying figures. Thus:

Figure 1 shows in front perspective view a preferred embodiment of the installation of this invention.

Figure 2 is a rear perspective of the installation of Figure 1.

Figure 3 is a rear perspective of the installation in the embodiment of Figure 1 with the supporting bracket removed and showing a cable in retracted, wound in position.

Figure 4 is a rear schematic view of a winder assembly in the embodiment of Figure 1.

Figure 5 is a schematic diagram of electrical connections in the installation of Figure 1.

Detailed description of an embodiment of the invention

[032] The following description and drawings are illustrative and are not to be construed as limiting. Numerous specific details are described to provide a thorough understanding of the presently disclosed embodiments. However, in certain instances, well-known or conventional details are not described in order to avoid obscuring the description. References to one or an embodiment in the present disclosure are not necessarily references to the same embodiment; and, such references mean at least one.

[033] Reference in this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments but not other embodiments.

[034] The installation of the invention is adapted for installation in a cavity formed in a wall of a structure, such as a building, using methods similar to those applicable to conventional power point installations. When installed, the installation is concealed behind a cover plate having apertures through which operable control devices are accessible. The power socket is provided within a body that is adapted for gripping by a human user, so that the body can be pulled away from the installation, in the process unwinding the power cord to which it is attached. The cord is unwound to be paid out from an elongate rotating cylinder which has a ratchet and pawl mechanism to lock against retraction the cord, unless the pawl is released by the user by means of a push button release.

[035] Like numbering of parts and features is used in Figures 1 to 5, which illustrate a preferred embodiment of the invention in differing views. The retractable cable installation is generally denoted by the number 10. It has an exposed front cover plate 12, which is fastened to a mounting bracket 14 having a front frame plate 16, which is connected to sides 18, 20. The bracket is adapted for installation within a wall cavity (not shown). It may also be installed within a housing (also not shown) which can be mounted to a wall surface. The bracket is made of galvanised iron, but may be of any suitable alternative. Cover plate 12 in this embodiment is of polyvinyl chloride (PVC), but may be manufactured from any suitable alternative in other embodiments.

[036] In this embodiment, front cover 12 has apertures for protrusion of a rocker-type on/off power switch 22, a thermal reset switch 24, a cable retraction activation button 26 and fastening screws 28, whereby cover plate 12 is fastenable to frame front plate 16. Instead of screws, alternative fastenings may be used. These may include resistance clips, by way of a non-limiting example, and similar friction or mechanical devices. [037] A female power socket body 30 of standard electrode configuration is held to be accessible on the exposed face of the cover plate 12. The power socket arrangement illustrated in this embodiment is of the 3-prong slitted kind 32 used in Australia, but can be replaced by standard socket configurations according to local requirements, including two-prong versions, when the invention is implemented in other jurisdictions.

[038] The electrode receivers within socket body 30 are electrically connected to a 3-core cable 34, visible in Figure 3, in which side walls 18, 20 of bracket 14 are shown removed for convenience. Cable 34 is additionally protected by a grippable insulating outer sleeve 36 just prior to its entrance to and connection with socket body 30. Body 30 has formation 38 on its side for assisting with gripping by a user.

[039] For storage, cord is wound on to a receiving drum 40, which has a helically grooved surface 42, as shown in Figure 4. The grooves are wide enough to receive snugly within them the coils 34b of the wound up cord. Drum 40 is rotatable on axle 44, which is fixedly mounted to sides 18, 20 of bracket 14.

[040] With reference to Figure 2, a cover 46 is clipped to mating formations (not visible) to secure it in operative position to protect cord 34 and to help guide it into the helical groove of surface 42. The guide/cover is not shown in Figures 3 and 4. The distal end of cord 34 is connected to a snap action switch (not shown) in electrical junction box 50.

[041] The sides 18, 20 of bracket 14 have extending upper 56 and lower 58 flanges having fastening holes 60 therethrough, to receive fastenings such as screws or bolts (not shown) and the like for securing the bracket and the installation in operative position.

[042] A user, wishing to bring the power socket to a location remote from the installation point, will grip the socket body 30 and pull it away from cover plate 12, drawing out with it from the bracket a length 34a of cord 34. The drawing action imparted on to cord 34 causes drum 40 to rotate on axle 44 and allow unwinding of the cord. A tensioning spring 48 connecting axle 44 to drum 40 provides resistance to the cord being unwound and serves to draw the cord back in. To prevent rewinding when not desired, mounted to the axle at the opposite end of the drum is a cord-arresting mechanism, in the form of ratchet 52 and pawl 54, allowing the cord to be unwound but preventing it being wound back automatically. Pawl 54 is connected to the release button 26 (see Figure 1 ) exposed through cover plate 12 to be accessible to the user. When the user wishes to store the cord after use, the user depresses button 26, which is mechanically coupled to pawl 54 and causes it to be lifted from ratchet wheel 52 temporarily. While the button remains depressed by the user, the energy of spring 48 is able to cause rotation of drum 40 in the opposite direction to the paying out direction, thereby to wind in the cord, so that it settles in helical groove 42, under guidance from guide plate 46.

[043] The power point is energized only if cord 34 has been unreeled fully. This is achieved installing a normally open snap action switch 62 in junction box 50, the switch being sensitive to a actuator 64 that is fixed to cord 34 at a point near to its proximal end, being the end opposite to the end connected to socket body 30. The proximal end is connectable to the external power supply at a terminal block 66 on box 50. The electrical switching arrangement is schematically depicted in the diagram of Figure 5. Box 50 is not shown in Figure 3, for ease of explanation.

[044] When the cord is unwound fully, actuator 64 is displaced from the switch, causing the switch to close the electrical connection to socket body 30. When the cord is wound back, the actuator re-enters the actuation zone associated with the snap action switch and, as a result, the switch opens again.

[045] The user is able to switch power to the socket body on an off using a toggle switch 22 of conventional design. Of course, power will be supplied only if the snap action switch 62 is not open. The cord therefore needs to be fully unwound before the socket of body 30 is in live condition. A further safety device is a thermal switch 24, which opens if temperature in the cord or in the installation exceeds a pre-set threshold, indicating a hazard arising from a possible fault. [046] Throughout this specification, plural instances may implement components, operations, or structures described as a single instance. Although individual operations of one or more methods are illustrated and described as separate operations, one or more of the individual operations may be performed concurrently, and nothing requires that the operations be performed in the order illustrated. Structures and functionality presented as separate components in example configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements fall within the scope of the subject matter herein.

[047] Some embodiments may be described using the expression “coupled” and “connected” along with their derivatives. For example, some embodiments may be described using the term “coupled” to indicate that two or more elements are in direct physical or electrical contact. The term “coupled,” however, may also mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other. The embodiments are not limited in this context.

[048] In addition, use of the “a” or “an” are employed to describe elements and components of the embodiments herein. This is done merely for convenience and to give a general sense of the invention. This description should be read to include one, or at least one, and the singular also includes the plural, unless it is obvious that it is meant otherwise.

[049] Upon reading this disclosure, those of skill in the art will appreciate still additional alternative structural and functional designs for a system and a process for an wall-mountable retractable extension cord installation through the disclosed principles herein. Thus, while particular embodiments and applications have been illustrated and described, it is to be understood that the disclosed embodiments are not limited to the precise construction and components disclosed herein. Various modifications, changes and variations, which will be apparent to those skilled in the art, may be made in the arrangement, operation and details of the method and apparatus disclosed herein without departing from the spirit and scope defined in the appended claims.