AU2003200998A1 - Plug-in protection device and secure method of permanently connecting plug-in electrical equipment to mains supply - Google Patents

Description

PLUG-IN PROTECTION DEVICE AND SECURE METHOD OF PERMANENTLY CONNECTING PLUG-IN ELECTRICAL EQUIPMENT TO MAINS SUPPLY This invention relates to plug-in protection devices for the protection of electrical appliances and equipment powered from mains supply power outlets, and to a secure method of connecting plug-in electrical devices, appliances and equipment to mains supply power outlets.

BACKGROUND OF THE INVENTION Electrical appliances and equipment are widely used in the home, office and work environment, and are very often powered from mains supply to which they are connected by plugging into power outlets. Although the power distribution boards of the above mentioned premises provide protection for the premises power circuits in the form of fuses and circuit breakers, these protection devices are intended to primarily protect circuit wiring from possible overloading and short circuits. Thus electrical appliances and equipment plugged into power outlets of these circuits very often do not have any dedicated protection of their own and are therefore at considerable risk of suffering major damage and failure should the appliances or equipment develop electrical faults. For example, a mm2 wiring for a power circuit supplying a number of 10 amps rated power outlets may be protected by a circuit breaker of 20 amps at the distribution board where the circuit originates. If an electrical appliance with a rated current of 8 amps is plugged into a power outlet of that circuit and develops an electrical fault, the appliance could overload to say 15 amps without tripping the 20 amps circuit breaker at the distribution board. Thus both the power outlet and the electrical appliance would not be protected against electrical and heat damage as their current ratings are exceeded whilst the risk of a fire starting or the total failure of the electrical appliance and power outlet is increased. This situation in which electrical appliances and equipment are operated without appropriate and dedicated electrical protection is disadvantageous and potentially dangerous.

Furthermore, some plug-in electrical appliances and equipment such as room air-conditioners, refrigerators and pumps can be damaged if mains voltage is outside of the rated voltage range of these appliances and equipment. Again, it is realised that it is disadvantageous to operate these appliances and equipment without proper dedicated over and/or under voltage protection.

OBJECTS OF THE INVENTION It is therefore an object of this invention to overcome the shortcomings of prior art protection systems by providing dedicated plug-in type protection devices for plugging into power outlets for the protection of plug-in type electrical appliances and equipment against damage caused by adverse conditions such as equipment overload or out-of-range mains supply voltage.

It is another object of this invention to provide a secure method of permanently connecting dedicated plug-in overload and out-of-range voltage protection devices of this invention to mains wiring. Thus, the possibility that the plug-in devices may be lost, misplaced, or that the devices may become poorly connected to mains through inadvertent dislodgment of the devices from their fully engaged positions into power outlets, is eliminated.

2 It is obvious that the secure method of this invention for permanently connecting plug-in protection devices to mains supply is not limited to the plug-in devices of this invention and can be applied to any electrical equipment that can suitably be encased and fitted with a power plug or similar connecting device for plugging into power outlets. Therefore, it is yet another object of this invention to provide a secure method for permanently connecting encased plug-in type electrical appliances and equipment to mains wiring.

BRIEF SUMMARY OF THE INVENTION In one aspect the present invention relates to a plug-in current overload protection device comprising: a casing enclosing an overload protection device such as a fuse, a circuit breaker or a thermal overload relay; earth, neutral and active metal prongs on one face of the casing for insertion into the respective earth, neutral and active receptacles of a mains supply power outlet; corresponding earth, neutral and active receptacles fitted with metal contact sleeves on another face of the casing for receiving the matching plug of an electrical appliance or equipment; metal connecting parts for establishing direct electrical connection between the earth prong one face of the casing and the corresponding metal sleeve of the earth receptacle on the other face of the casing; metal connecting parts for establishing direct electrical connection between the neutral prong one face of the casing and the corresponding metal sleeve of the neutral receptacle on the other face of the casing; metal connecting parts for establishing direct electrical connection between the active prong on one face of the casing and the first terminal of the overload device, and metal connecting parts for establishing direct electrical connection between the second terminal of the overload device and the metal sleeve of the corresponding active receptacle on the other face of the casing.

In another aspect the present invention relates to a voltage sensitive plug-in protection device comprising:a casing enclosing a voltage sensitive protection device such as an over-voltage, an under-voltage or a combined over and under voltage protection device with switching output capabilities; earth, neutral and active metal prongs on one face of the casing for insertion into a mains supply power outlet; corresponding earth, neutral and active receptacles fitted with metal contact sleeves on another face of the casing for receiving the matching plug of an electrical appliance or equipment; metal connecting parts for connecting the over-voltage, the under-voltage or the combined over and under voltage protection device to the neutral and active wiring of the power outlet; metal connecting parts for establishing direct electrical connection between the earth prong on one face of the casing and the metal sleeve of the corresponding earth receptacle on the other face of the casing; metal connecting parts for establishing direct electrical connection between the neutral prong on one face of the casing and the metal sleeve of the corresponding neutral receptacle on the other face of the casing; metal connecting parts for establishing direct electrical connection between the active prong on one face of the casing and the first terminal of the output switch of the over-voltage, the under-voltage or the combined over and under voltage protection device, and 3 metal connecting parts for establishing direct electrical connection between the second terminal of the output switch of the over-voltage, under-voltage or the combined over and under voltage protection device and the metal sleeve of the corresponding active receptacle on the other face of the casing.

In yet another aspect the present invention relates to a plug-in current overload or over-voltage and/or under-voltage protection device as described above that is provided with fixing means for securely attaching the plug-in protection device to the power outlet into which the protection device is plugged, or to the structure to which the power outlet is fixed. Thus, the plug-in protection device of this invention becomes permanently connected to mains wiring and is also prevented from being lost or becoming poorly connected to mains supply through inadvertent dislodgment of the device from its fully engaged position into the power outlet.

The secure method of this invention for permanently connecting plug-in protection devices to mains supply is not limited to the plug-in protection devices of this invention. The method can advantageously be applied to any electrical equipment, provided that the equipment can be suitably encased and fitted with connecting means for plugging into a power outlet, so as to prevent the inadvertent dislodgment or loss of the electrical equipment. Other advantages will become obvious when the descriptions of the embodiments are read in conjunction with the accompanying drawings. Therefore, it is yet another object of this invention to provide a secure method for permanently connecting encased electrical equipment, fitted with connecting means for plugging into power outlets, to mains wiring. This object of this invention is achieved by providing the encased plug-in electrical equipment with fixing means for securely attaching the electrical equipment to the power outlet or to the structure to which the power outlet is fixed.

It is to be noted that several obvious variations from the above-described devices of the present invention are possible without departing from the intent of the invention. Examples are given below which exemplify some of these possible variations and it is to be understood that the scope of the present invention encompasses all possible variations described or implied.

Some electrical equipment do not require an earth connection and therefore plug-in protection devices and electrical equipment of this invention can be manufactured to only connect to the active and neutral wiring of power outlets.

Some power outlets do not have provision for an earth connection and again the plug-in protection devices and electrical equipment of this invention can be manufactured to only connect to the active and neutral wiring of these power outlets.

Descriptions given above all have the interrupting devices such as fuses, circuit breakers, overload relays and output switches of over-voltage and/or under-voltage protection devices connected in series with the active wiring. It is obvious that connecting the same fuses, circuit breakers, overload relay or output switches in series with the neutral wiring would have the same effect of de-energising the electrical appliance or equipment if they were to operate. However, it must be emphasised that this practice, although workable in providing the required equipment protection, is dangerous as it would result in the electrical appliance or equipment remaining connected to mains active wiring after the appliance or equipment is de-energised following the operation of the protection device.

4 Power outlet and equipment plug configurations vary from country to country and it is the intent of the present invention to include plug-in protection devices manufactured to suit any power outlet and plug configuration.

Although plug-in protection devices described above are either overload or voltage sensitive protection devices, it is the intent of this invention that the plug-in protection devices may include any combination of the above mentioned types of protection.

DESCRIPTIONS OF THE EMBODIMENTS Embodiments of the invention are given in the following sub-sections of this specification and are illustrated by the accompanying drawings. The invention however, is not limited to the embodiments described or to the drawings illustrating them. The intent of the embodiments and the accompanying drawings are merely to illustrate how the invention may be put into effect and are not to be understood as being limiting on the invention.

First embodiment for a plug-in over-current protection device The first embodiment of the invention is depicted by FIG.1 through to FIG.5. FIG. 1 is a front view of the plug-in over-current protection device comprising of a casing of insulating material such as PVC or similar. On its front face the plug-in protection device includes earth, neutral and active receptacles fitted with metal sleeves for the purpose of making contact with the corresponding earth, neutral and active metal prongs of a matching appliance plug connected to the plug-in protection device. The front face also includes the reset switch of a circuit breaker contained within the casing of the plug-in protection device.

FIG. 2 is a side view of the over-current protection device showing the circuit breaker reset switch on the device front face, and earth, neutral and active metal prongs on the device rear face. FIG. 3 is a rear view of the plug-in protection device and shows the arrangement of the earth, neutral and active metal prongs on the rear face of the device for connection to a matching power outlet.

FIG. 4 is a side view showing how the plug of an electrical appliance, the plug-in protection device, and a wall mounted mains power outlet are all interconnected. Thus, it is realised that as long as the switch of the power outlet is closed and the circuit breaker has not tripped, the arrangement depicted by FIG. 5 connects the electrical appliance or equipment to mains supply.

The operation of the over-current protection device is best explained by referring to the schematic diagram of FIG. 5. The earth and neutral metal prongs on the rear face of the plug-in protection device are connected to the metal sleeves of the respective earth and neutral receptacles on the front face of the plug-in protection device by metal connecting parts A and B respectively. Metal connecting parts C connect the active metal prong on the rear face of the plug-in protection device to the first terminal TI of the circuit breaker, whilst metal connecting parts D connect the second terminal T2 of the circuit breaker to the metal sleeve of the active receptacle on the front face of the plug-in protection device. Thus, when the rear face metal prongs of the plug-in protection device are plugged into a mains power outlet and the metal prongs of an appliance plug top are plugged into the front face receptacles of the plug-in protection device, the current drawn by the appliance flows through the normally closed contact CC of the circuit breaker. This contact opens to de-energise the electrical appliance if the trip current setting of the circuit breaker is exceeded. Once the circuit breaker has tripped, the appliance remains de-energised until the reset switch on the front face of the plug-in protection device is operated.

It is realised from the above description that the circuit breaker of a plug-in protection device can be suitably rated to provide dedicated over-current protection for an electrical appliance or equipment.

Second embodiment for a plug-in voltage sensitive protection device The description of the second embodiment is very much the same as that of the first embodiment with the following exceptions: The plug-in protection device incorporates a voltage sensitive protection device, such as an over-voltage, an under-voltage or a combined over and under voltage protection device, instead of the circuit breaker of the first embodiment.

Referring to FIG. 6, which is the schematic diagram for the voltage sensitive protection device of the second embodiment, it can be seen that the normally closed output switch DD of the over-voltage, the undervoltage or the combined over and under voltage relay replaces the normally closed contact of the circuit breaker of the first embodiment.

The over-voltage, the under-voltage or the combined over and under voltage relay of the second embodiment requires connection to both the active and neutral wiring in order for the supply voltage to be ascertained and compared with the relay voltage trip settings. Thus FIG. 6 shows additional metal connecting parts E connecting the neutral metal prong on the rear face of the plug-in protection device to a third terminal T3 of the over-voltage, under-voltage or combined over and under voltage relay of the plug-in protection device.

The contact of the over-voltage, the under-voltage or the combined over and under voltage relay opens to de-energise the electrical appliance if the supply voltage is detected to be over or under the set threshold trip values of the relay as the case may be. Once the relay has tripped, the appliance remains de-energised until the reset switch on the front face of the plug-in protection device is operated.

It is realised from the above description that the over and/or under voltage relay of a plug-in protection device can be suitably rated to provide appropriate dedicated over and/or under voltage protection for an electrical appliance or equipment.

Third embodiment for a plug-in over-current protection device permanently fixed to a power outlet The third embodiment for a plug-in over-current protection device is as depicted by FIG. 7 through to FIG. 11. FIG.7 is a front view of the plug-in over-current protection device which is identical to that described for the first embodiment except that the casing of the protection device of the third embodiment has two additional side extensions having a fixing hole each. FIG. 8 is a three dimensional view of the plug-in over-current protection device showing the spatial relationship between the casing of the plug-in protection device and its two side extensions with fixing holes. The distance between the centres of the fixing holes of the plug-in protection device of either FIG. 7 or FIG.8 is the same as the distance between centres of the fixing holes of the power outlet of FIG. 9 which shows the front view of the power outlet. The fixing holes of the plug-in protection device are located so that when the plug-in protection device of this embodiment is plugged into a suitable power outlet, the two fixing holes of each of the plug-in protection device and those of the power point are aligned.

FIG. 10 shows the front view of the plug-in protection device of the third embodiment plugged into a power outlet. When connected to a suitable power outlet the plug-in protection device is securely fixed to the 6 power outlet by two screws through the sets of aligned fixing holes of the plug-in protection device and the power outlet. FIG. 11 is a side view showing how the plug of an electrical appliance, the plug-in protection device, and a wall mounted power outlet are all interconnected.

It is therefore realised from the above description that by securely fixing the plug-in protection device of this embodiment to the power outlet into which the plug-in protection device is plugged, the plug-in protection device becomes permanently connected to mains supply and is prevented from being lost or becoming poorly connected to mains supply through the inadvertent dislodgment of the device from its fully engaged position into the power outlet.

Fourth embodiment for a plug-in over-current protection device securely fixed to the surface or structure on which a power outlet is mounted The fourth embodiment for a plug-in over-current protection device is as depicted by FIG. 12 through to FiG.12 is a front view of the plug-in over-current protection device that is electrically identical to that described for the first embodiment. Referring to FIG. 13 which shows a sectional view of the plug-in protection device, it can be seen that the casing of the plug-in protection device is different to the casing of any previously described embodiments in that it has two compartments. These are a front compartment C2 housing the overcurrent protection device and a rear open compartment C1 containing an electrical plug. The electrical plug of compartment C 1 is connected to the over-current device of compartment C2 by a short flexible cable. FIG. 14 is a rear view of the plug-in protection device and shows the electrical plug and the short flexible cable of compartment C1. FIG. 14 also shows the mounting flange surrounding the open end of compartment CI which is provided with fixing holes for securely fixing the plug-in protection device of this embodiment to the surface to which a power outlet is fixed.

Referring to FIG. 15, it is realised that, since the dimensions of the open end of compartment Cl of the plug-in protection device are greater than those of the power outlet into which the plug-in protection device is plugged, the plug-in protection device can be securely fixed permanently to the surface on which the power outlet is mounted. FIG. 15 shows how the flange surrounding compartment C2 of the plug-in protection device is used to securely fix the plug-in protection device to the wall using screws S. Thus the plug-in protection device of this embodiment becomes permanently connected to mains supply and is prevented from being lost or becoming poorly connected to mains supply through the inadvertent dislodgment of the device from its fully engaged position into the power outlet.

Fifth embodiment for a plug-in 4 way power board using the secure fixing method described for the fourth embodiment The fifth embodiment typifies how a plug-in electrical equipment can be permanently connected to mains supply using the method described for the fourth embodiment.

Plug-in power boards are common and generally have an electrical cord and plug for connecting to a power outlet. These devices are generally left unsecured on the floor or desk and are a problem during cleaning.

The power boards themselves are known to gather carpet lint and dust and require frequent cleaning to maintain them in full operational order. In an attempt to solve these problems, some manufacturers provide power boards 7 that can be fixed to the wall but the unsecured electrical cords of these power boards have the disadvantage of being unsightly.

Power boards are also the cause of accidents through tripping over their power cord. A further disadvantage of existing power boards is that they can easily be lost or become poorly connected to mains supply through the inadvertent dislodgment of the plug of the device from its fully engaged position into the power outlet.

The fifth embodiment for a 4 way plug-in power board is as depicted by FIG. 16 and FIG.17. FIG. 16 is a front view of the 4 way plug-in power board comprising of four individually switched outlets. FIG. 16 also shows the mounting flange and fixing holes of the plug-in power board.

Referring to FIG. 17 which shows a sectional view of the 4 way plug-in power board, it can be seen that the casing of the plug-in power board is similar to the casing of the fourth embodiment previously described in that it has two compartments. These are a front compartment C2 housing the four outlets and switches of the plugin power board and a rear open compartment Cl containing an electrical plug. The electrical plug of compartment Cl is connected to the outlets and switches of the front compartment C2 by a short flexible cable.

Referring to FIG. 17, the dimensions of the open end of compartment C1 of the plug-in power board are greater than those of the power outlet into which the plug-in power board is plugged so that the plug-in power board can be securely fixed permanently to the surface on which the power outlet is mounted. As for the fourth embodiment, the flange surrounding compartment C2 of the plug-in power board is used to securely fix the plugin protection device to the wall using screws. Thus the plug-in power board of this embodiment becomes permanently connected to mains supply and is prevented from being lost or becoming poorly connected to mains supply through the inadvertent dislodgment of the plug of the plug-in power board from its fully engaged position into the power outlet.

As the plug-in power board of this embodiment is mounted on the wall and completely encloses the power outlet the electrical plug and the cord, it is obvious that the other previously mentioned disadvantages of existing plug-in power boards are overcome by the plug-in power board of this embodiment.

Sixth embodiment for a plug-in carbon monoxide alarm using the secure fixing method described for the fourth embodiment The sixth embodiment further demonstrates how a plug-in electrical equipment can be permanently connected to mains supply using the method described for the fourth embodiment.

Mains powered plug-in carbon monoxide alarms are common and are of two different types, namely: Plug-in carbon monoxide alarms fitted with a short length of electrical cord and a plug. These carbon monoxide alarms are designed for wall mounting in the vicinity of the power outlet into which they are plugged.

Plug-in carbon monoxide alarms for direct plugging into a power outlet. This type of carbon monoxide alarm has metal prongs moulded onto one face of the alarm device which match the receptacles of a suitable power outlet, thus eliminating the use of an electrical cord.

A first disadvantage of currently available plug-in type carbon monoxide alarms is that they are required to be plugged into an unswitched power outlet so that power to the alarm device cannot be inadvertently switched off Often this means that an electrician needs to be called in to change a switched power outlet to one which is unswitched, change which has cost implications.

A second disadvantage of currently available plug-in carbon monoxide alarms is that, even if they are plugged into an unswitched power outlet, the risk that these devices become disconnected from mains through inadvertent unplugging is very real.

A third disadvantage of currently available plug-in carbon monoxide alarms is that these alarm devices may be lost or become poorly connected to mains supply through the inadvertent dislodgment of the plug of the alarm devices from their fully engaged position into the power outlet.

A further disadvantage of plug-in carbon monoxide alarms fitted with an electrical cord and plug is that the exposed cord is unsightly.

The sixth embodiment for a plug-in carbon monoxide alarm is as depicted by FIG. 18 through to FIG. 18 is a front view of the plug-in carbon monoxide alarm which has air sampling louvres, a test switch, a power on indicator light and additional louvres for an audible alarm device on its front face. FIG. 18 also shows the mounting flange and fixing holes of the plug-in carbon monoxide alarm of this embodiment.

Referring to FIG. 19 which shows a sectional view of the plug-in carbon monoxide alarm, it can be seen that the casing of the plug-in power board is similar to the casing of the fourth embodiment previously described in that it has two compartments. These are a front compartment C2 housing the carbon monoxide alarm and a rear open compartment Cl containing an electrical plug. The electrical plug of compartment C1 is connected to the carbon monoxide alarm of the front compartment C2 by a short flexible cable.

Referring again to FIG. 20, the dimensions of the open end of compartment Cl of the plug-in carbon monoxide alarm are greater than those of the power outlet into which the plug-in alarm device is plugged. Thus the plug-in carbon monoxide alarm can be permanently fixed to the surface onto which the power outlet is mounted. As for the fourth embodiment, the flange surrounding compartment C2 of the plug-in carbon monoxide alarm is used to securely fix the alarm device to the wall using screws. FIG. 20 is another sectional view showing the plug-in carbon monoxide alarm of this embodiment mounted on a wall and covering the power outlet into which the carbon monoxide alarm is connected.

From the above description it is realised that all the previously mentioned disadvantages of currently available plug-in carbon monoxide alarms are overcome, namely: The switch of the power outlet is made inaccessible so that the installation of plug-in carbon monoxide alarms of this invention is not restricted to unswitched power outlets only.

Since the electrical plug of the carbon monoxide alarm and the power outlet into which it is plugged are totally enclosed and inaccessible, the risk that these devices become disconnected from mains through inadvertent unplugging is eliminated.

The plug-in carbon monoxide alarm is securely and permanently fixed to the wall onto which the power outlet is mounted, and as the electrical plug of the alarm device and the power outlet are totally enclosed and inaccessible, the carbon monoxide alarm of this invention cannot be lost or become poorly connected to mains supply through the inadvertent dislodgment of the plug of the alarm device from its fully engaged position into the power outlet.

The short flexible cable connecting the electrical plug to the carbon monoxide alarm is totally enclosed within the rear compartment of the carbon monoxide alarm and is therefore out of sight.

9 Seventh embodiment for a plug-in bathroom clock, radio and power outlet combination unit using the secure fixing method described for the fourth embodiment The seventh embodiment is another example of how a plug-in electrical equipment can be permanently connected to mains supply using the method described for the fourth embodiment. In the case of the seventh embodiment, three items of electrical equipment are grouped into one combination unit of the plug-in type, namely a mains powered clock, a mains powered radio and a switched mains power outlet.

Plug-in mains powered clocks and radios fitted with flexible cable and plug find widespread use in bathrooms and are often the cause of electrocution and death in the house. This usually is as a result energised electrical equipment falling into water whilst their power cord and plug remain connected to mains supply. The seventh embodiment overcomes this disadvantage by eliminating the above mentioned risk of electrocution in bathrooms from plug-in mains powered clocks and radios.

The seventh embodiment for a combined plug-in clock, radio and switched power outlet unit for bathrooms is as depicted by FIG. 21 through to FIG.23. FIG.21 is a front view of the plug-in combination unit showing a clock face, a switched power outlet, a radio volume control, a radio tuning control and tuning frequency scale as well as a set of radio loudspeaker louvres on the front face of the combination unit. FIG. 21 also shows the mounting flange and fixing holes of the plug-in combination unit of this embodiment.

Referring to FIG. 22 which shows a sectional view of the plug-in combination unit, it can be seen that the casing of the plug-in combination unit is similar to the casing of the fourth embodiment previously described in that it has two compartments. These are a front compartment C2 housing the switched power outlet, the clock and the radio of the plug-in combination unit, and a rear open compartment C1 containing an electrical plug. The electrical plug of compartment Cl is connected to the switched power outlet, the clock and the radio of the front compartment C2 by a short flexible cable.

Referring again to FIG. 22, the dimensions of the open end of compartment Cl of the plug-in combination unit are greater than those of the power outlet into which the plug-in combination unit is plugged.

Thus the plug-in combination unit can be securely fixed permanently to the surface onto which the power outlet is mounted.

As for the fourth embodiment, the flange surrounding compartment C2 of the plug-in combination unit is used to securely fix the plug-in combination unit to the wall using screws. FIG. 23 is another sectional view showing the plug-in combination unit of this embodiment mounted on a wall and covering the power outlet into which the plug-in combination unit is plugged.

From the above description it is realised that the previously mentioned disadvantage of using existing plug-in radios and clocks in bathrooms is overcome as the radio and clock of the combination unit are permanently fixed to the bathroom wall and cannot fall into water.

Eighth embodiment for a plug-in carbon monoxide alarm using the secure fixing method described for the fourth embodiment The eighth embodiment is depicted by FIG. 24 which shows a section of a carbon monoxide alarm connected to a power outlet. This embodiment is identical to the sixth embodiment except for the following: A spacer with its front and rear ends open is used to provide the space required to house the short flexible cable, the plug and the power outlet. Thus compartment C1 does not form part of the carbon monoxide alarm and is the enclosed space of the spacer.

Additional screws are used to fix the carbon monoxide alarm to the spacer.