EP0952638A1

EP0952638A1 - Bipolar electric plug equipped with switch

Info

Publication number: EP0952638A1
Application number: EP98830245A
Authority: EP
Inventors: Nicola Cassano
Original assignee: MURTAS EUGENIO
Current assignee: MURTAS EUGENIO
Priority date: 1998-04-23
Filing date: 1998-04-23
Publication date: 1999-10-27

Abstract

An electric bipolar plug (1) comprises a body (2) made of an insulating material, two male type contact pins (3,4) extending partially out of the body (2) able to contact, inside the plug, electric conductors (7,9) of a user equipment, and outside the plug, correspondent contact pins of a bipolar outlet, and a switch (10) that interrupts the electric connection between at least one (7) of the electric conductors and a correspondent contact pin (3) of the plug.

Description

The present invention relates to a bipolar electric plug of the type utilised to connect a user equipment to a wall outlet of a civil or industrial electrical installation.
A well known bipolar electric plug normally comprises an electrically insulating body, plastic or ceramic, and at least two male contact pins partially extending out of the body, each having a connecting terminal for the connection to electric conductors of a power cord of a user equipment.
A second type of bipolar electric plug, normally known as adapter plug, comprises, besides the insulating body and the male contact pins, also two female contact pins, reachable from outside the body, able to receive corresponding male pins of a second plug.
Inside this plug the female pins are electrically connected to the male pins.
Adapter plugs are necessary when the power cord of the user equipment is provided with an electric plug different from the outlet to be used.
In fact exist, also within individual countries, several standard electric plugs and outlets, normally coupled to electric equipment of different powers.
A user equipment which does not absorb from the electrical installation so much current can in fact utilise a small electric plug, while high power equipment, like electric ovens, heaters, washing machines or dish-washing machines, need plugs and outlets of larger dimensions, able to manage higher currents without overheating.
Power plugs have in fact bigger contact pins, more spaced, and they always have a third contact pin used for the safety connection of the equipment to ground.
The ground contact pin could have same shape and dimensions as the other pins of the plug and being positioned centrally between other pins, or being realised by means of a female type pin or alternately as a plurality of thin conducting plates.
Known electric bipolar plugs are currently used to connect, through a power cord, the user equipment to the electrical installation.
Some equipment has an internal switch which allows to interrupt one or both the power conductors which supply current to the equipment itself.
High power equipment are normally in this category, like electric ovens, electric heaters, washing machines or dish-washing machines.
Many other equipment instead are not equipped with a general switch.
Are in this second category for instance refrigerators or freezers, whose switching on and turning off are controlled by a thermostat, and generally the electronic equipment of the last generation.
For example in television sets, in video-recorders, in computers and monitors, power supply is managed by a dedicated electronic circuit that controls also switching on and off and therefore it is not always present a general switch on the supply cables.
This allows the user to switch on the television or the video-recorder through a remote control, or switch on the computer through a keyboard's key or again allows the computer to turn off the monitor when not used by the operator and, if necessary, also to switch it on again.
An other example of equipment that doesn't have a power switch regards those electric or electronic equipment that have an external power supply unit, usually contained in a small package provided with a plug.
Are in this category generic power supplies for low voltage equipment, 3, 6, 9 or 12 Volts, power supplies for radio, recorders, handheld calculators and chargers for rechargeable batteries, for example for cellular telephones.
For this second category of equipment is therefore necessary, to be sure that the equipment is switched off, to unplug it from the outlet.
If in many cases this isn't a problem, as for refrigerators or freezers that normally stay always switched on, for other equipment could be necessary to switch completely off the power supply, when not in use, in order to avoid an useless heating of the same and an useless small current consumption.
An other drawback that could derive from disconnecting, after each use, the equipment's plug from the outlet, is the possible deterioration of the contact pins of the outlet, specially in case of frequent and repeated uses.
A first object of the present invention is therefore to solve the problem of how to allow to switch off of an electric equipment, not provided of a power switch, or however without using his internal switch.
These and other purposes are achieved by an electric plug realised according to the invention, as claimed in the attached claims.
The plug according to the invention can advantageously be used in substitution of a known type plug or, in the adapter version, can be joined to a plug present in the equipment.
The above and other objects of the invention will result more clear from the description of a preferred embodiment with reference to the accompanying drawings in which:

the Figure 1 shows inside an electric plug according to a first embodiment of the present invention;
the Figure 2 shows inside an electric plug according to a second embodiment of the present invention;
the Figure 3 illustrates a first scheme of the inside electric connections of a plug according to the present invention;
the Figure 4 shows inside an electric plug according to a third embodiment of the present invention;
the Figure 5 illustrates a second scheme of the inside electric connections of a plug according to the present invention; and
the Figure 6 shows, in a perspective view, an electric plug according to the present invention.

With reference to Figure 1 an electric bipolar plug 1, realised according to the present invention, comprises a body 2 made of an insulating material, a first 3 and a second 4 contact pin and a switch element 10.
The insulating body 2 is realised in plastic material, in ceramic material or in any highly insulating resin.
The contact pins 3 and 4 extends partially out of the body 2 in order to contact, outside the plug, corresponding contact pins of a bipolar outlet not visible in figure, and they present each, on the extremity inside the plug, a terminal 11, 13 for the connection of an electric conductor of a power cord 14 of a user equipment.
The switch element 10 interrupts the electric connection between one 7 of the conductors of the cable 14 and the terminal 11 of the correspondent contact pin of the plug.
The switch 10 is inserted partially in the body 2 in such a way to be operable from outside the plug.
A user can therefore act directly on the switch of the plug in order to switch on or off the connected equipment.
The electric plug of Figure 1 also comprises a third contact pin 5 which extends partially out of the body 2 in an intermediary position between the first two contact pins.
The third contact pin 5 is a ground pin which contacts, inside the plug, a ground electric conductor 8 of the user equipment, and outside the plug, a ground contact pin of a corresponding bipolar outlet.
In Figure 2 is instead shown a second embodiment of a plug according to the present invention.
An electric bipolar plug 21, of the adapter type, comprises a body 22 made of an insulating material, two contact pins 27,29 of female type, two contact pins 23 and 24 of male type and a switch element 30.
The two female contact pins 27,29 are inserted in the body 22 and accessible from the outside of the plug, while the two male contact pins 23,24 extends partially out of the body 22.
The insulating body 22 is realised in plastic material, in ceramic material or in any highly insulating resin.
The switch element 30 interrupts the electric connection between a female contact pin 27 and the correspondent male type contact pin 23 inside the plug.
The second female contact pin 29 is instead in electric contact with the correspondent male type pin 24.
The switch 30 is partially inserted in the body 22 in a such way to be operable from outside the plug itself.
The user can operate directly the switch present in the adapter plug to switch on or off the connected equipment.
The electric plug of Figure 2 as well comprises a third contact pin 25, that partially extends from the body 22, placed in an intermediary position between the first two contact pins.
Such pin 25 is a male ground pin connected, inside the adapter plug 22, to a correspondent ground female contact pin 28.
In Figure 3 is illustrated a scheme of the electric connections inside a plug according to the present invention, as illustrated in Figures 1 and 2 and previously described.
Particularly it could be noticed a portion 40 showing the three male contact pins and a portion 41 showing the three electric conductors of the plug of Figure 1 or, alternatively, the three female contact pins of the plug of Figure 2. A switch 42 interrupts the electric connection between one of the male type contact pins and a corresponding conductor or contact pin of female type.
In Figure 4 is shown a third embodiment of a plug according to the present invention.
The main elements of the plug 61 of Figure 4 are fundamentally the same elements as those of the plug shown in Figure 1, an insulating body 62, three male contact pins 63, 64 and 65 equipped with a terminal for contacting electric conductors of a power cord 74 and a switch element 70.
The switch element 70 is, differently from the switch 10 of Figure 1, a bipolar type switch.
The switch 70 interrupts contemporaneously the electric connection between both the electric conductors 67 and 69 of the cable 74 of a user equipment and correspondent contact pins 63 and 64 of the plug.
A ground electric conductor 68 is connected to a ground contact pin 65 of the plug.
In Figure 5 is illustrated a scheme of the internal electric connections of the plug shown in Figure 4.
A circuit block 50 points out the three male contact pins of the plug while a block 51 points out the three conductors of the equipment's cable.
A bipolar switch 52 interrupts the electric connection between both the contact pins of male type of the plug and the corresponding conductors of the cable.
The plug realised according to this third embodiment allows to switch off the user equipment connected to the plug isolating it from the electrical installation, maintaining for safety only the ground connection.
Analogously also in the adapter plug shown in Figure 2 could be incorporated a bipolar switch that interrupts both connections between the female conductor pins and the male ones, getting the same functionality as the plug of Figure 4.
The Figure 6 show, in a perspective view, a plug 80, as previously described and illustrated in Figures 1 or 4, coupled to a power cord 82 of a user equipment and incorporating a switch 81 for switching on and off the same equipment.

Claims

Bipolar electric plug (1) comprising a body (2) made of an insulating material, at least two male type contact pins (3,4), extending partially out of the body (2) and able to contact, inside the plug, electric conductors (7,9) of a user equipment, and outside the plug, correspondent contact pins of a bipolar outlet, characterised in that it comprises a switch element (10) for interrupting the electric connection between at least one (7) of said conductors and the correspondent contact pin (3) of the plug.
Electric plug according to claim 1, characterised in that the switch element (10) is incorporated in the insulating material body (2) and it is operable from outside the plug.
Electric plug according to claim 2, characterised in that the element switch (10) is a bipolar type switch that interrupts the electric connection between both electric conductors (7,9) and the correspondent contact pins (3,4) of the plug.
Electric plug according to claim 2 or 3, characterised in that it comprises also a third contact pin (5), extending partially out of the body (2) and able to contact, inside the plug, a ground electric conductor (8) of a user equipment, and, outside the plug, a ground contact pin of a corresponding bipolar outlet.
Bipolar electric plug (21) comprising a body (22) made of an insulating material, at least two female type contact pins (27,29) accessible from outside the body (22), at least two male type contact pins (23,24), extending partially out of the body (22) and able to contact, inside the plug, said female type contact pins (27,29), characterised in that it comprises a switch element (30) for interrupting the electric connection between at least one (27) of said female type contact pins (27,29) and the correspondent male type contact pin (23) of the plug.
Electric plug according to claim 5, characterised in that the switch element (30) is incorporated in the insulating material body (22) and it is operable from outside the same plug.
Electric plug according to claim 6, characterised in that the switch element (30) is a bipolar switch that interrupts the electric connection between both the female type contact pins (27,29) and the correspondent contact pins of male type (23,24) of the plug.
Electric plug according to claim 6 or 7, characterised in that it also comprises a third female contact pin (28), accessible from outside of the body (22), and a third male contact pin (25), extending partially out of the body (22) and able to contact a ground contact pin in a corresponding bipolar outlet, in electric contact with said third female contact pin (28).