SAFETY PLUG

Abstract: The present invention relates to an apparatus (10) for supplying current to electric appliances. More specifically the invention concerns a construction of a plug that will minimise the risk for plug damage and human bodily harm. Said apparatus (10) comprises a device casing (12) and an interchangeable adapter plug (14) which are joined to one operating unit. The device casing (10) is covering and protecting electronic current supplying components and carries a first electrical connector (20) and a second electrical connector (22). The interchangeable adapter plug (14) has an adapter plug casing (28) with electrical connector pins (30) and an adapter plug connector (24) that is connectable with said first electrical connector (20) of the device casing (12). The apparatus has moment device (50) that helps the device casing (12) to separate from the interchangeable adapter plug (14) irrespective of the orientation of a pulling force acting on said device casing.

Description: SAFETY PLUG FIELD OF THE INVENTION The present invention relates to an apparatus for supplying current to electric appliances. More specifically the invention concerns a construction of a plug that will minimise the risk for plug damage and human bodily harm. BACKGROUND OF THE INVENTION Differing plug configurations have posed a problem to manufacturers of electric supply devices and battery chargers. While many electrical devices are sold for use throughout the world, there is no world standard for electrical plug configurations, size, shape, position or numbers of pins. Plug diversity is also a significant problem for people who travel to different parts of the world and have to take electrical devices with them, particularly devices such as phones and computers. The traditional solution for the mechanical configuration problem is to provide an interchangeable adapter plug which includes a socket to accommodate the pins of the electrical device, such as a transformer or battery charger, integrated with a second set of pins on a configuration for a local socket or wall outlet. In US 5540596 a device is described for supplying electrical current to electric appliances, especially mobile appliances. The device has a plug housing equipped with an electric plug, which houses the electrical and electronic components supplying the current. To simplify the use of the device with various electric socket configurations, several interchangeable adapter plugs are provided which can be releasably attached to the plug housing. Each adapter plug has connector pins that are shaped and arranged according to electric socket configurations used in various countries. The adapter housing has connector springs which are electrically coupled to the connector pins and which connector corresponding current supply connector surfaces carried by the plug housing. The plug housing has a recess into which a tongue of an electronic circuit board protrudes and on which the connector surfaces are formed. The adapter housing fits into the depression so that the connector springs engage the connector surfaces of the circuit board when assembled. A releasable snap-on lock formed by the adapter housing and the plug housing secures the two to each other. When the device is not in use a closure is releasably placed over the recess to protect it against damage and contamination . Alternating current (AC) is supplied from the wall outlet to the electric device, e.g. a battery charger. The alternating current could cause injuries to humans and animals and therefore it is necessary to design the electric device so high currents not is exposed if the device has been misused. In a charger for electrical equipment such as mobile phones, AC current at 110-220 voltage (V) is transformed to direct (DC) current at 2-8 V. The DC current is conducted from the charger through a flexible cord or cable to the connected equipment. This flexible cord has to withstand pulling and bending. Therefore it is necessary to provide means for strain relief to the cord input and fastening. However, if the cord is pulled with a high force when it is applied to a wall outlet this pulling force will give rise to a high force level and moment on the charger, its pins and on the wall outlet. The charger will act as a lever arm. Today's known power suppliers and battery chargers having an interchangeable adapter plug are fixed with slots, grooves and plastic snapping. The plug is fixed without any flexibility to the housing of the charger or the power supplier. The whole effect of the force from the cord will be conducted by the charger or power supplier causing damage and malfunction especially to the adapter plug, pins and wall outlet when the force is high enough. As an example could one of the pins of the plug be broken and left into the wall outlet. There have been accidents when a user has been badly injured trying to take a broken pin out of an outlet without switching the electricity off first. SUMMARY OF THE INVENTION One problem to be solved is to reducing the resulting forces and strains on different parts of an electric power supply device having interchangeable modular plugs when the device is sitting directly in an AC wall outlet and the device is exposed to an unsymmetrical force or load. Another problem to be solved is how to design an electric power supply device, for an example a power supplier or charger device, having a device casing and interchangeable modular plugs where said plugs not is assembled to said device casing by fastening devices like locks, latches, grooves, snappings or closures. One object of the invention is to reduce the resulting forces and strains on different parts of the device when the plug is sitting directly in the AC wall outlet and the device is exposed to unsymmetrical forces or loads. Another object is to design a power supplier device or charger device having interchangeable modular plugs where said device casing and plug lack any recesses, ducts, grooves or closures. Just another object of the invention is to increase security against accidents causing fires, death and bad injures. Said problems are solved by providing an apparatus having an adapter plug with a moment device that limits the necessary force on a device casing for separating said device casing from the adapter plug. In more detail an moment device helps the device casing to separate from the interchangeable adapter plug irrespective of the orientation of a pulling force acting on said device casing . One of the advantages over known technique is that the invention will minimise the risk for malfunction due to high forces and loads acting on the supply device. There will be no visible or touchable current conducting parts after the device casing has been separated from the adapter plug still sitting in the wall outlet. The costs for manufacturing the power supply devices will decrease by eliminating details like recesses, ducts, grooves, locks, snappings, latches or closures. Cord strain relieves that are used for securing a connection between the cord and a device casing could also be eliminated. The invention will now be described in more detail with reference to preferred embodiments thereof and also with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure la illustrates a side view of a prior art electric power supply device for supplying current to an electric appliance . Figure lb shows the prior art adapter plug only. Figure lc is a side view of the prior electric power supply device stuck into a wall mounted electrical socket when a DC cord in the opposite end of the device is very roughly pulled. Figure 2 shows a side view of an embodiment of the invented apparatus . Figure 3 shows a side view of an embodiment of an invented adapter plug separated from the device casing. Figure 4 is a view of the connector side of the same invented embodiment as in figure 3. Figure 5 illustrates how the invented apparatus works when the cord connected to an electric power supplied appliance is roughly pulled. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Figure la illustrates a side view of a prior art electric power supply device 10 for supplying current to an electric appliance. Said device 10 comprises a device casing 12 and an interchangeable adapter plug 14 which are joined and firmly fixed together with a plug cover 16 and a latch 18 to the device casing 12. The device casing 12 is covering and protecting current supplying electronic components. A first electrical connector 20 and a second electrical connector 22 are electrically coupled to the components. The connectors, 20 and 22, are mounted on a circuit board and protrude through said casing 12. An adapter plug connector 24 is connectable and removable to said first electrical connector 20. A flexible cord 26 has a cord connector 34 which is connected to the second electrical connector 22 and conducts electrical power to an electrical appliance (not shown) . The cord 26 has a strain relief 32 to reduce damage risk on the cord connector 34 and the second electrical connector 22. Figure lb shows a view of the connector side of an prior art adapter plug only. Said plug includes an adapter plug casing 28, electrical connector pins 30, a locking device (a snapping means) 18 and an adapter plug connector 24. The adapter plug connector 24 is arranged in a substantially right angle to the orientation of the electrical connector pins 30. Figure lc illustrates a side view of the prior art electric power supply device 10 stuck into a wall mounted electrical socket 42. The flexible cord 26 is exposed to a force pulling the device's upper end, where the second connector 22 is situated, away from the wall 40. The adapter plug 14 is more or less locked to the socket 42 in the wall 40 and the device casing 12 is locked to the adapter plug 14. The device casing 12 will act as a lever arm. If a damaging force have an unfortunate orientation and the plug 14 doesn't release from the socket 42 the plug will break. This could cause that conducting parts having dangerous electric power become visible and possible to touch by humans. Other parts of the power supply device could also be damaged, e.g. the second electric connector, components, soldered details or the casing of the device. The wall 40 and the socket outlet 42 are drawn with dashed lines. Figure 2 shows the different parts of an embodiment of an invented apparatus for supplying current to an electric appliance. The apparatus comprises an device casing 12 and an interchangeable adapter plug 14, which are joined by connecting connector means, 20 and 24, to one operating unit 10 without any locking or snapping device. The device casing 12 covers and protects current supplying electronic components. The electronic components are arranged on a printed circuit board having first and second electrical connectors that are electrically coupled to the components and carried by said casing. The first electrical connector has pins 20, which are protected by the device casing 12. A flexible cord 26 for supplying power to an appliance is connected to said second connector 22. There is no need for strain relief means attached between the cord and said connector. A moment device 50 between the device casing 12 and the adapter plug 14 will support the device casing 12 to separate from the interchangeable adapter plug 14 irrespective of the orientation of a pulling force acting on said device casing. Figure 3 is a side view of an embodiment of the invented interchangeable adapter plug 14 that is separated from the device casing 12. This modular plug 14 has an adapter plug casing 28, electrical connector pins 30 and an adapter plug connector 24. Said connector 24 is removable and connectable with said first electrical connector 20 of the device casing 12 and protrudes from the adapter plug casing 28 at an substantially right angle to the electrical connector pins 30. Said pins 30 are operatively connected to the adapter plug connector 24 by conducting parts into the plug casing 28. These pins 30, which often is called prongs, differs in amount, shape and arrangement between different plugs. One user chooses that adapter plug that suits into the pin receiving openings of the electrical socket or wall outlet that he wants to use for charging or power supplying. The device casing 12 and the interchangeable adapter plug 14 are joined only by the first electrical connector 20 and the adapter plug connector 2 . The first electrical connector 20 include an electrically conducting sleeve means which is protected by a cover. This cover could be manufactured in a more flexible material than the rest of the casing. The first electrical connector 20 comprises electrical conducting pins that is stuck into the sleeve during the assembling of the device casing 12 and the adapter plug 14. The device casing 12 and the interchangeable adapter plug 14 are kept together by the friction between the sleeve means of the adapter plug connector 24 and the pins of the first electrical connector 20. The strength of force necessary to divide the connectors is called the release force. It is possible to control the release force by varying width and height of the moment device. Said release force is depending on the friction between the sleeves of the socket and the pins. It is possible to vary the release force by designing the plug connector and the casing connector. Figure 4 is a view of the connector side 46 of the same invented interchangeable adapter plug 14 as in figure 3. The adapter plug 14 has a moment device 50 that helps the device casing 12 to separate from the interchangeable adapter plug 14 irrespective of the orientation of a pulling force acting on the device casing 12 or the cord 26. The design of the adapter plug 14 limits the necessary force on the device casing for separating said device casing 12 from the adapter plug casing. The moment device 50 is attached to the adapter plug casing 28 and bears on the outer edge of the device casing. The crossing between the moment device and the connector side wall 46 is marked with a dashed line. This embodiment of the moment device 50 is a designed edge applied to the adapter plug casing 28 surrounding the adapter plug connector 24. The connector side wall may be designed cup-shaped and the connector means is possible to place anywhere inside this moment device 50. The moment device in figure 3 and figure 4 is designed to fit the outer dimensions of the apparatus casing. That means that the height and the width measures of said casing is the same. However, the width and the height of the moment device 50 can be varied within the scoop of this invention. In another embodiment of the invented apparatus the moment device 50 is attached to the adapter plug casing 28 and bears anywhere on the first connector side 44 of the device casing 12 inside said sides outer edge. Just another embodiment of the invented apparatus is to attach a moment device 50 to the first connector side 44 of the device casing 12 which bears on the adapter plug connector side wall 46. Just another embodiment of the invented apparatus is to attach a first moment device 50 to the first connector side 44 of the device casing 12 and a corresponding second moment device 50 on the adapter plug connector side 46 that bears on said first moment device 50. The apparatus casing needs no recesses, ducts, grooves or closures. It simplifies the design of the casing very much. Figure 5 illustrates how the invented apparatus works when the cord 26 connected to an electric power supplied appliance is roughly pulled. The moment device 50 acts like a support to the device casing 12 when the casing 12 raises and the pulling force divides the first connector 20 from the adapter plug connector 24 without any damages. The device casing 12 pivots standing on the moment device 50. The adapter plug 14 will still sit in the wall socket 42 but there will be no dangerous conductors exposed. The wall 40 and the socket outlet 42 are drawn with dashed lines.

Claims: CLAIMS 1. Apparatus for supplying current to an electric appliance, said apparatus comprising a device casing and an interchangeable adapter plug which are joined to one operating unit, said device casing is covering and protecting electronic current supplying components, said device casing carrying a first electrical connector and a second electrical connector , said interchangeable adapter plug having an adapter plug casing with an adapter plug connector, which is connectable with said first electrical connector of the device casing, and electrical connector pins which are operatively connected with the adapter plug connector, shaped and arranged for insertion in pin receiving openings of an electrical socket, c h a r a c t e r i s e d in that, a moment device helps the device casing to separate from the interchangeable adapter plug irrespective of the orientation of a pulling force acting on said device casing. 2. Apparatus according to claim 1, c h a r a c t e r i s e d in that, said moment device is attached to the adapter plug casing and bear on the outer edge of the device casing. 3. Apparatus according to claim 1 or 2, c h a r a c t e r i s e d in that, the device casing and the interchangeable adapter plug are joined only by the first electrical connector and the adapter plug connector. 4. Apparatus according to claim 3, c h a r a c t e r i s e d in that, the device casing and the interchangeable adapter plug are kept together only by the friction between the sleeves of the adapter plug connector and the pins of the first electrical connector. 5. Apparatus according to claim 1, c h a r a c t e r i s e d in that, the adapter plug connector protrudes from the adapter plug casing at an substantially right angle to the electrical connector pins. 6. Apparatus according to claim 1, c h a r a c t e r i s e d in that, a flexible cord 26 for supplying power to an appliance is connected to said second connector 22. 7. Apparatus according to claim 6, c h a r a c t e r i s e d in that, the apparatus is a power supply device. 8. Apparatus according to claim 7, c h a r a c t e r i s e d in that, the apparatus is a battery charger. 9. Apparatus according to claim 7 or 8, c h a r a c t e r i s e d in that, the apparatus is connected to a mobile radio communication device or a mobile personal computer device.

Inventors: HEDLUND THOMAS J, HEDLUND, THOMAS, J.
Applicants: ERICSSON TELEFON AB L M, TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)
Application year: 1999
Main classification: H01R13
IPC codes: H01R13, H01R31