AU4008697A

AU4008697A - An electrical plug

Info

Publication number: AU4008697A
Application number: AU40086/97A
Authority: AU
Inventors: Tat-Kwong Cheung
Original assignee: Koontat Dev Co Ltd
Current assignee: KOONTAT DEVELOPMENT Co Ltd
Priority date: 1997-07-08
Filing date: 1997-08-28
Publication date: 1999-02-08
Also published as: HK1007402A2; WO1999003171A1; AU691152B3; KR19990007812U; JP3052059U; CN1260073A; JP2001510278A; CN1102299C; KR200257567Y1

Description

WO 99/03171 PCT/CN97/00088 AN ELECTRICAL PLUG FIELD OF THE INVENTION This invention relates to an electrical plug, and in particular to such a 5 plug adapted to be used in a confined space. BACKGROUND OF THE INVENTION This invention relates to an electrical plug of the type used to connect electrical appliances, for example domestic electrical appliances such as 10 lights, television sets, audio equipment and so on, to wall sockets. Wall sockets are somewhat unsightly and there is a tendency for them to be located behind items of furniture such as tables, cabinets, bookcases and so on, or often there is nowhere to put an item of furniture other than in front of a socket. 15 Such sockets can still be used, especially for appliances that are relatively fixed and do not require regular plugging and unplugging from the su,.t. However such situations do present difficulties. Most notably conventional electrical plugs tend to be relatively thick and therefore a 20 correspondingly large space must be left between the wall and the item of furniture to accommodate the plug. This space is both wasted and unsightly. A number of attempts have been made to mitigate this problem by reducing the thickness of the electrical plug. 25 Examples include US Design Patent 375,291 where the electrical wires are connected to a thin plug body through a pivoting connection so that the wires can lie flat against the wall rather than extending outwardly therefrom in use. US 5,454,731 and EP 0589881A also disclose arrangements in which 30 a flat "low-profile" plug body is provided with the wires being connected WO 99/03171 PCT/CN97/00088 thereto in such a manner that they extend parallel to the wall. Another example is to be found in US 4,857,013. One difficulty with very thin low-profile plugs, however, is that 5 they can be difficult to remove from the socket after use because the plug body does not allow a user to get a good grip on the plug so as to exert the necessary force to remove the plug from the socket-especially since there is often a fairly tight fit between the plug and the socket. 10 US 5,454,731 and US 4,857,013 attempt to solve this problem by providing pivoting pull tabs that may be moved out of a flat position to extend at an angle to the wall and which may be used to pull the plug from the socket. These arrangements can be disadvantageous, however, in that they may cause a large amount of stress to be placed on the pull tabs 15 potentially leading to breakage. SUMMARY OF THE INVENTION It is an object of the invention to provide a flat low-profile plug having an improved means for facilitating removal of the plug from a socket. 20 According to the present invention therefore there is provided an electrical plug comprising a plug body having first and second parts, said first part being formed with electrical pins for insertion into a socket, and said second part surrounding said first part and being adapted to move 25 telescopically with respect thereto. By means of this arrangement the plug body may normally be thin and have a low-profile for easy accommodation in a confined space, but when it is desired to remove the plug from a wall socket the second part may be 30 moved telescopically with reference to the first so as to expand the size of the plug to facilitate a user gripping the plug to remove it from the socket. 2 WO 99/03171 PCT/CN97/00088 Preferably the direction of the telescoping movement is parallel to the axes of said pins and thus parallel to the direction of movement of the plug when it is desired to remove the plug from the socket. Other directions of 5 telescoping movement may also be possible, however, provided that there is at least a significant component of movement in a direction parallel to the pin axes. Preferably the first and second parts are of substantially the same 0 thickness and the second part is movable between a first position in which the second part completely surrounds the first part, and a second position in which the first part is substantially completely exposed. In this way the effective size of the plug body can be almost doubled by telescopic sliding of the second part from its first to second positions. 5 Preferably the first and second parts are provided with means for preventing mutual separation of the two parts. Such means may , for example, comprise mutually engaging portions formed on said first and second parts. 20 Preferably the first part of the plug body is provided with a surrounding wall in which is provided an aperture for the electrical wires to pass therethrough. The electrical wires make contact with the pins within the first part of the plug body. The second part of the plug body may likewise be 25 provided with a corresponding aperture for the passage of wires therethrough. In a particularly preferred embodiment the first and second parts of the plug body each comprise a generally tubular portion formed with an annular 30 wall, the second part having a greater diameter than the first part so that it can surround the first part , and wherein the wall of the first part is 3 WO 99/03171 PCT/CN97/00088 provided with at least one channel extending parallel to the axis of the first part, and the wall of the second part is provided with at least one lug adapted to be received in the channel for sliding movement therein. Preferably both annular walls are provided with apertures to permit a cable to pass therethrough. BRIEF DESCRIPTION OF THE DRAWINGS Some embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 is a perspective view from above of an electrical plug according to an embodiment of the invention with the plug in a flat unexpanded condition, Fig.2 is a view corresponding to Fig. 1 but from underneath the plug, Fig3 is a view corresponding to Fig. 1 but with the two parts of the plug body moved apart, and Fig.4 is a view corresponding to Fig.3 but from underneath the plug. >PREFERRED EMBODIMENT OF THE INVENTION Referring to Figs. 1 to 4 there is shown a preferred embodiment of an electrical plug according to the present invention. The plug comprises generally circular first 1 and second 2 parts. The first part 1 comprises a base portion and electrical pins 3 pass therethrough. In the embodiment shown in 5 the figures the pins 3 are three flat pins, but it will be appreciated that any other form or number of pins may be provided. The form of the first part 1 is a shallow generally tubular body with a side wall 4. An aperture 5 is provided in the side of wall 4 for the passage ) into the interior of the plug of an electrical power cable 6 comprising 4 WO 99/03171 PCT/CN97/00088 individual wires (live, neutral and earth) 7 which are connected to the pins 4 in a conventional manner (not shown). The first part 1 is also formed with an annular flange portion 8 extending around the circumference of the base of the first part 1 and forming a smooth extension of the undersurface of the plug. The second part 2 of the plug is also in the form of a generally shallow tubular body formed with a wall portion 9. The circumference of wall portion 9 is, however, slightly larger than corresponding wall portion 4 of the first part 1 such that the first part 1 can be received within the second part 2 as shown in the figures. Wall portion 9 also includes an aperture 10 corresponding in size and location to aperture 5 again so that an electrical cable or lead can pass therethrough into the interior of the plug. It should be noted, however, that aperture 10 is formed with an open side towards the base of the plug body so that the second part can still move relative to the first as will be described below. As can be seen particularly clearly in Fig.4 the first part 1 of the plug is also formed with three channels 11 defined in the wall portion 4 at 120 ° intervals. The channels extend for the length of the tubular body portion of the first part 1 of the plug generally parallel to the axis of the part 1 and therefore parallel to the axes of the pins 3 and thus parallel to the direction of insertion/extraction of the plug from a socket. The wall 9 of the second part 2 is likewise formed with three corresponding inwardly directed lugs 12 that are sized so as to fit within channels 11 and slide therealong. Although not clearly visible in the figures, the end of the wall 4 of the first part 1 remote from the flange portion 8 is formed with corresponding fixed outwardly engaging projections. The upper surface of the second part 2 is formed in any desired manner. It may for example be completely closed, or may be provided with a decorative manner as shown in the Figures. 5 WO 99/03171 PCT/CN97/00088 The operation of the plug will now be described. The two parts 1,2 are movable between a first position shown in Figs. 1 & 2 in which the second part 2 surrounds the first part 1 with the wall 9 of the second part 2 resting on the flange 8 of the first part and surrounding the wall 4 of the first part 1. In this position the plug is in a thin low-profile condition and takes up as little space as possible. However, when it is desired to extract the plug from a socket the size of the plug can be increased to make it easier by sliding the second part 2 relative to the first part 1 in a telescopic manner with the lugs 12 sliding along channels 11 until they are stopped by the fixed projections formed on the first part 1. In this way the size of the plug can increase by a factor of almost two providing a much larger plug with a greater surface area that is easier to hold and pull so as to facilitate extraction from a socket. Of course the present invention is not limited to the embodiment described. Not only - as mentioned above - may the form of the pins vary to take into account differing standards in different countries, but also the manner in which the telescopic movement is achieved may of course also vary. For example, another possible embodiment would be to provide the exterior surface of wall 4 and the interior surface of wall 9 with a simple screw thread such that the two parts 1,2 may be moved together or apart by a screw action. The embodiment described, however has the advantage that only a single simple pulling movement is necessary, and furthermore that movement is in the direction of the extraction of the plug from a socket in any event so the action required to enlarge the plug may be all part of the extraction process. 6

Claims

1. An electrical plug comprising a plug body having first and second parts, said first part being formed with electrical pins for insertion into a socket, and said second part surrounding said first part and being adapted to move telescopically with respect to the first part.

2. An electrical plug as claimed in claim 1 wherein the direction of telescopic movement is parallel to the axes of the electrical pins.

3. An electrical plug as claimed in claim 1 wherein said first and second parts are of substantially the same height.

4. An electrical plug as claimed in claim 1 wherein said second part is 5 movable from a first position in which the second part completely surrounds the first part, and a second position in which the first part is substantially completely exposed.

5. An electrical plug as claimed in claim 1 wherein said first and ) second parts are provided with means for preventing mutual separation thereof.

6. An electrical plug as claimed in claim 5 wherein said separation prevention means comprises mutually engaging portions formed on said first 5 and second parts.

7. An electrical plug as claimed in claim 1 wherein each of said first and second parts are provided with means for permitting access of an electrical cable into said plug. 8

8. An electrical plug as claimed in claim 1 wherein said first and 7 WO 99/03171 PCT/CN97/00088 second parts each comprise a generally tubular portion formed with an annular wall, said second part having a greater diameter than said first part, and wherein said wall of said first part is provided with at least one channel extending parallel to the axis of said first part, and said wall of said second part is provided with at least one lug adapted to be received in said at least one channel for sliding movement therein.

9. An electrical plug as claimed in claim 8 wherein each said wall is provided with an aperture to permit passage therethrough of an electrical cable.

10. An electrical plug as claimed in claim 8 wherein said first part is formed with an annular flange adjacent its lowermost surface. 8