GB2199705A

GB2199705A - An electrical plug incorporating a time switch

Info

Publication number: GB2199705A
Application number: GB08800408A
Authority: GB
Inventors: Mark William Meakings
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-01-09
Filing date: 1988-01-08
Publication date: 1988-07-13
Also published as: GB8800408D0

Abstract

An electrical plug (2) comprising a body (6) incorporating a switch (14) for preventing the flow of electricity from the plug, and a timer (16). for causing the switch to operate after a predetermined period. The timer may include a battery back- up, a reset for resetting the timer and an override switch. A cut-out may prevent flow of electricity if the timer (16) fails to operate the switch (14) at the end of a set period. <IMAGE>

Description

AN ELECTRICAL PLUG This invention relates to an electrical plug.

As is well known, electrical plugs are employed to connect domestic, office and industrial appliances to the mains electricity. As is also well known, sometimes persons using the appliances forget to turn them off with the result that over-heating of the appliance may occur.

This in turn may lead to the outbreak of a fire.

It is an aim of the present invention to obviate or reduce this problem.

Accordingly, this invention provides an electrical plug comprising a body having front and rear faces, at least two pins projecting from the front face of the body, switch means for preventing the flow of electricity from the plug, and timer means for causing the switch means to operate after a predetermined period.

The electrical plug may be used to provide electricity to domestic appliances such for example as irons, fires, hair dryers, televisions, video apparatus, radios, cookers, lights, drills and generally all domestic appliances requiring electricity. Similarly, the plug may also be used to provide electricity to all types of machinery used in offices and factories, and also used in land, sea and air vehicles. Any desired length of time can be set on the timer means to ensure that the plug will only operate for a predetermined period of time so that, for example, it may be possible to set up to twelve hours in the timer means in one quarter hour intervals.

The switch means may be an electro-mechanical switch or it may alternatively be an electrical solid state switch such for example as a switching transistor arrangement.

The timer means may be set by timer setting buttons.

Other devices may of course be employed to set the timer means if desired.

Preferably, the plug includes a timer display arrangement.

The timer display arrangement may be for displaying the time initally set on the timer means and/or the time that the plug has been in use.

The plug can be arranged to have a digital display panel on its rear face.

The timer display arrangement may be button operated.

The plug may include a battery for powering the timer display arrangement when the plug is not in use.

The battery may be a re-chargable battery, in which case the plug will usually be such that the battery is automatically re-charged during use of the plug.

Alternatively, the battery may be of the non-rechargable disc type battery that is currently employed in watches.

The plug may include reset means for resetting the timer means for example if the plug is in use longer than the time set on the timer means.

The reset means may be arranged to operate automatically consequent upon the plug being plugged into a socket. The automatic operation of the reset means may be arranged to take effect either consequent upon the plug receiving electricity from the socket or alternatively due to the mechanical insertion of the plug in the socket.

Alternatively, the reset means may be a manually operated reset switch. The manually operated reset switch is preferably a button operated switch but other types of switch may be employed if desired.

The plug may include an over-ride switch. The over-ride switch may be used-to bypass the switch means and the timer means so that the plug may then operate substantially as a known standard type of electrical plug.

The over-ride switch may be employed if there is a malfunction in the electrical plug, such for example as in the timer means or if a battery should be employed and the battery should have become discharged.

The over-ride switch is preferably a button operated switch but other types of switch may be employed if desired.

The plug may include back-up cut-out means for preventing the flow of electricity from the plug consequent upon failure of the timer means to operate the switch means at the end of the time period set in the timer means.

The back-up cut-out means may include a relay.

The pins will usually be of rectangular or circular cross section but they may obviously be of other cross sectional shapes if desired. Depending upon the type of appliance to be connected, the plug may have two or three pins. Usually the plug will have three pins.

The body may be in two portions. The two portions may be held together by a screw or screws.

The plug will normally include the usual terminal devices for connecting electrical wires to the plug.

These terminal devices may be screw and cylinder arrangements or they may be screwless connections such for example as friction connections.

The plug will usually include clamp means for clamping an electrical lead to the plug.

The clamp means may be a bridge member and a pair of screws. Alternatively, the clamp means may be one or more flexible gripper members which are such that they flex and grip the electrical lead. Other types of clamp means may also be employed.

The plug will also usually include fuse receiving means for receiving a fuse. Various known constructions of fuse receiving means may be employed. Usually the fuse will be connected to the positive pin in accordance with usual plug technology.

The plug may be sold with or without a fuse.

An embodiment of the invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 is a top plan view showing the inside of a plug; Figure 2 shows a rear face of the plug; and Figure 3 shows an electrical circuit for the plug.

Referring to the drawings, there is shown an electrical plug 2 comprising a body 4. The body 4 has a front face (not shown) and a rear face 6. An earth pin 8, a neutral pin 10 and a live pin 12 project from inside the body 4 as shown in Figure 1 through the front face of the body 4.

The plug 2 is provided with switch means 14 for preventing the flow of electricity from the plug 2. The plug 2 is also provided with timer means 16 for causing the switch means 14 to operate after a predetermined time period. Time is set in the timer means 16 by means of two timer setting buttons 18, 20. The timer setting buttons 18, 20 are located inside the body 4 of the plug 2 and they project through the rear face 6 of the plug 2 as shown in Figure 2.

Time set on the timer means 16 is shown in a timer display panel 22 which forms part of a timer display arrangement. The timer display panel 22 may show an hours and minutes time display for the time actually set in the timer means 16, and it may also be arranged to show the time that the plug has been in use. Such a digital display enables a user of the plug 2 easily to see all required information. The hours and minutes time display for the time set in the timer means and the time display for the time the plug has been in use can be arranged to be displayed simultaneously or sequentially.

If a sequential display is required, then one of the time set buttons 18, 20 or another button (not shown) may need to be depressed to cause the sequential display.

The timer means 16 includes a battery (not shown) for ensuring that a display can still be achieved when the plug 2 is not being used. Thus the battery will enable a time to be set in the timer means 16 and to be checked without the necessity for plugging the plug 2 into a socket.

The plug 2 includes reset means in the form of a reset button 24 for resetting the timer means 16 if the plug 2 is used for a longer period than set on the timer means.

The reset means in the form of the reset button 28 is a manually operated reset means. If the time set on the timer means 16 is not exceeded during use of the plug, then the timer means is reset to zero automatically on the next use of the plug. Thus, when the time set is-not exceeded, the user of the plug is not required to do anything out of the ordinary and the plug 2 can be used like a standard known plug.

The plug 2 includes an over-ride switch in the form of an over-ride button 26. The over-ride button 26 can be operated to by-pass the switch means 14 and the timer means 16 so that the plug 2 can then operate as a normal three pin plug. The over-ride button 26 may be operated in the event of a malfunction of the switch means 14 or the timer means 16, or in the event of the battery in the timer means 16 becoming over discharged.

As shown in Figure 3, the circuit of the plug 2 also includes a back-up cut-out switch 28 for preventing the flow of electricity from the plug 2 consequent upon failure of the timer means 16 to operate switch means 14 at the end of a time period set in the timer means 16. The switch 28 is associated with a relay 30 so that the switch 28 and the relay 30 together form back-up cut-out means.

As shown in Figure 1, the plug 2 includes a fuse 32, an earth terminal 34 to which an earth wire 36 is connected, a neutral terminal 38 to which neutral wires 40, 42 are connected, and a live terminal 44 to which live wires 46, 48 are connected Referring now to Figure 3, the various live, neutral and earth connections are shown by the letters L, N, E.

When the plug 2 is plugged into an electrial socket and the socket is switched on, the earth connection is via line 50 shown in Figure 3. With the reset button 24 operated, current can pass along lines 52, 54, 56 to the live pin 12. A contactor device 58 will be such that the circuit is completed to the live pin 12 via a contact 60.

When the time set on the timer means 16 lapses, current passes along lines 62, 64 to open the switch means 14 and to stop current passing along lines 66, 68. A solenoid 70 which was holding contact 60 closed no longer receives current and the contact 60 is spring biased to its open position so that current can no longer pass along line 56 to the live pin 12. Simultaneously, the manual reset button 24 is caused to move to its off position.

In the event of a failure in, for example, the timer means 16 or the switch means 14, the over-ride button 16 can be depressed to complete the circuit 72 shown in dotted lines and thus to continue to allow current to be supplied to the solenoid 70. Thus the contact 60 will remain in position and current will continue to be supplied to the live pin 12.

When the timer means 16 operates, current can also be arranged to.pass along line 74 to the relay 50. The relay, via line 76 can be arranged to operate the back-up cut-out switch 28-to provide back-up operation in case the switch means 14 should not have operated.

It will thus be seen that the plug 2 is able to have any desired time set in the timer means 16 such that the plug 2 will only operate for that time. At the end of the time set in the timer means 16, the plug 2 will not pass any more electricity to the appliance to which it is connected. By setting an appropriate time in the timer means 16, the risk of over heating of an appliance and the subsequent risk of fires due to the over heating can be avoided or reduced. By way of example, it is mentioned that a user of an iron may decide that the maximum time normally spent ironing is two hours. The two hours is thus set into the timer means 16 and then each time the iron is plugged in and switched on, the timer means 16 will start to record the time elapsed.Should the user go away and forget to switch off the electricity, after two hours the plug 2 will automatically switch off and the reset button 24 will pop out of the rear face 6 of the plug 2. This gives the user confidence that any appliance will not be left accidentally connected to the mains, thus eliminating or reducing the danger of over heating and fires as mentioned above. If the user is still ironing when the two hours lapse, the user can simply push in the reset button 24 to reconnect the supply and allow a further two hours of use. In the event that the iron should be switched off before the two hours have lapsed, then, when the plug 2 is next plugged in and the socket is switched on, the timer means 16 will automatically reset to zero.If the user should wish to alter the maximum time set in the timer means 16, then this can easily be done on the outside of the plug 2 using the timer setting buttons 18, 20.

Referring to Figures 1 and 2, the inside of the plug 2 is of a different design to a conventional three pin plug, the redesign being necessary to provide room for the switch means 14, the timer means 16 and the associated accessories. A benefit of the illustrated design is that when fitting an appliance, the live, neutral and earth wires from the cable 80 may all be cut to the same length, making fitting a simpler task. The cable 80 is held in position by clamp means in the form of a bridge member 82 and a pair of screws 84, 86. The body 4 is in two parts with the rear face 6 forming part of a plug cover as is known for conventional plugs. The plug cover is secured to the remainder of the body 4 by means of a screw 88 in a manner generally known for conventional plugs.

Providing the battery is functioning correctly, the plug 2 is preferably arranged such that, when the plug is in operation, the timer display panel 22 will show the time that the plug 2 has been in use. When the plug 2 is removed from circuit, then the timer display panel 22 can be arranged to display, either automatically or on activation of a switch, the maximum time period that has been set into the timer means 16. Thus any one looking at the plug 2 before connecting it to the mains, will be able to see how long a time the plug 2 is set for. In the event that the battery should go flat, the manual override button 26 can be operated and a suitable flashing message could appear in the timer display panel 22 to indicate that a new battery was needed. The timer display panel 22 can show a flashing "99:99"-whenever the plug is connected to the mains.

If the relay 30 is caused to operate, it will normally be arranged that the plug 2 can then only be operated if the over-ride button 26 is used. Without operating the over-ride button 26 it will be necessary to repair or replace the defective parts such for example as the timer means 16.

It is to be appreciated that the embodiment of the invention described above with reference to the accompanying drawings has been given by way of example only and that modifications may be effected. Thus, for example, the design of the inside of the plug may be different from that shown in Figure 1. Also, the plug could be such that it has only two pins. Generally, the plug 2 may be used in any situation where conventional plugs are used, with the advantage that the plug of the present invention provides increased safety. The plug may be generally modified to be used with different socket designs and different voltages in various countries and on land vehicles, ships and aircraft.

If desired, the timer means may operate via multiple switching. The timer means may be set to record times that the electrical plug is to be switched on and off, in relation to the twenty four hour clock, in a similar way to conventional time switches. The timer Ineans may be set to allow several different time periods to be stored for activation by the switch means. Advantageously, the timer means could allow for any timing program to be incorporated, which controls the switch means in -the electrical plug.

If desired, the switch means may be a thernal trip system, and may include, for example, a power supply means, a timer means as described above, a trigger device means, which may be a transistor, linked to a heater means, and a thermal trip means, which may be bi-metallic. The switch means may also contain any other suitable and approy,riate products for efficient operation, The switch means may also consist of either a triac or a relay system, or other suitable system.

It is envisaged that the plug may be sold under the trade mark CONFIDENCE PLUG.

Claims

1. An electrical plug comprising a body having front cid rear faces, at least two pins projecting from the front face of the body, switch means for preventing the flow of electricity from the plug, and timer means for causing the switch means to operate after a predetermined period.

2. An electrical plug according to claim 1 in which the switch means is an electro-mechanical switch, an electrical solid state switch, or a thermal trip switch 5. An electrical plug according to claim 1 or claim 2 in which the timer means is operated by timer setting buttons or by a multiple switching arrangement.

4. An electrical plug according to any one of the preceding claims in which the plug includes a timer display arrangement.

5 An electrical plug according to claim 4 in which the timer display arrangement is for displaying the time initially set on the timer means and/or the time that the plug has been in use.

60 An 2l-ectrical plug according to any one of the preceding claims and which has a digital display panel on its rear face.

7. An electrical plug according to any one of the preceding claims and including 'a battery for powering the timer display arrangement when the plug is not in use.

8. An electrical plug according to any one of the preceding claims and including reset means for resetting the timer means.

90 An electrical plug according to any one of the preceding claims and including an over-ride switch.

10. An electrical plug according to any one of the preceding claims and including back-up cut-out means for preventing the flow of electricity from the plug consequent upon failure of the timer means to operate the switch means at the end of the time period set iii the timer means.

11. An electrical plug according to any one of the preceding claims and including fuse receiving means for receiving a fuse.

12. An electrical plug substantially as herein described with reference to the accompanying drawings.