WO2005096107A1

WO2005096107A1 - Timer unit

Info

Publication number: WO2005096107A1
Application number: PCT/GB2005/001283
Authority: WO
Inventors: Andrew John Ekins
Original assignee: Andrew John Ekins
Priority date: 2004-04-01
Filing date: 2005-04-01
Publication date: 2005-10-13
Also published as: GB0621443D0; GB2429077A; GB0407455D0; GB2429077B

Abstract

A mains powered timer has a housing (10) having projecting conducting pins (12, 13, 14) arranged to permit the timer to be plugged into a standard mains electricity outlet. Connectors (19) are provided internally of the housing (10) for terminating a mains cable (26), and an electronic timer unit is arranged within the housing, to time a preset interval. The timer unit connects at least one conducting pin (12) to a corresponding connector (19) during timing of the pre-set interval. A manual start control (32) is accessible externally of the housing (10), to start timing of the pre-set period, and so permit the flow of electricity from the pins to the mains cable (26).

Description

TIMER UNIT This invention relates to a mains powered timer unit, adapted for connection to an electric mains outlet socket. Electric mains-operated timers are well-known. A common design has a housing having projecting conducting pins arranged as a plug with the pins arranged to permit the housing to be connected to a mains outlet socket. The housing also defines a socket of a similar configuration to that of the projecting pins, whereby a plug provided on the mains cable of an appliance may be connected to that socket in the housing. Within the housing, there is a timer unit which is arranged to switch on and off at pre-set times, so as to complete connections between the conducting pins of the housing and the corresponding receptors of the socket. In this way, an appliance plugged into the timer socket will be turned on and off at pre-set times. Many electric timers as described above are provided with override switches, which permit an appliance to be turned on other than by the timer unit. Some such timers also include a further switch arranged so that when operated, the connection between the projecting pins and the timer socket is broken, whereby an appliance plugged into the timer socket will not be energised, even if the timer unit turns on. Some timers of the kind described above use a mechanical timer unit, whereas others use an electronic module. In the case of the former, there are usually tappets which have to be moved in order to select the times of day when the timer is to turn on and off, and so also the duration of the on-period. An electronic module usually has to be programmed by following a complex series of button presses, in order to adjust the times of the day when the timer is turned on and off. As such, timers of the kind described above are not at all convenient to employ when an appliance is to be operated for a pre-set time interval, but starting at some indeterminate point. A particular problem arises in the domestic environment with an electrical appliance which includes a heating element, in order that it might fulfil its intended function. For example, a hair styling device may incorporate an electric heating element to raise the temperature of the device, for performing hair straightening, hair crimping and so on. An electric iron also incorporates a heating element, to raise the temperature of the sole plate of the iron. An electric blanket has a heating element embedded in the fabric of the blanket, again to raise the temperature in a bed when the blanket is connected to an electrical source. Not infrequently, people connect to the mains an appliance of the kind described above and then forget the appliance is connected. As such, the temperature of the appliance can rise beyond the intended maximum and there is a significant fire risk then attaching to the continued operation of the appliance. Though most appliances include some form of safety cut-out, as that may not operate during the life of the appliance, the reliability of the cut-out is at best questionable, and so it may not operate when needed. In order to increase safety in use and to minimise the risk of thermal runaway in the event the safety cut-out does not operate, it would be advantageous to restrict the time for which an appliance including a heating element may operate, but a timer of the kind described above is not suitable for restricting the operating time of an appliance. It is a principal aim of the present invention to provide a timer for an appliance which enables the energisation of an appliance for a pre-set period, following the initial supply of electricity to the appliance. According to the present invention, there is provided a mains-powered timer comprising a housing provided with conducting pins arranged to permit the timer to be plugged into a standard mains outlet, connectors internally of the housing for terminating a mains cable passing into the housing, an electronic timer unit provided within the housing and arranged to time a pre-set time interval, the timer unit connecting at least one conducting pin of the housing to a corresponding connector during timing of the pre-set interval, and a manually operable timer start control accessible from outside the housing and arranged to start the timing of said pre-set interval. It will be appreciated that the timer of this invention permits an appliance to which the timer is connected to be energised for a pre-set time interval, on demand. To achieve this, the mains cable of the appliance is essentially permanently wired to the timer so that the appliance may be connected to a mains outlet in just the same way as would be the case were the appliance mains cable provided with a conventional plug. However, as with a plug, the timer may be released from the mains cable by opening the housing and releasing the connectors to which the conductors of the mains cable are connected, so that the timer may then be used with some other appliance. When the appliance is to be energised for a pre-set period, the manual timer start control is operated, so initiating the start of a timed period. The timer unit makes a connection between at least one pin of the housing and the corresponding connector, such that a circuit is established between the fixed mains outlet socket and the appliance. The circuit is broken again at the expiry of the timed period, so turning off the appliance to which the timer is connected. Preferably, and for a timer intended for use on an unbalanced electric mains system where one conductor (usually referred to as the "live" conductor) of the mains is at a relatively high potential with respect to earth and the other conductor (usually referred to as the "neutral" conductor) is more or less at earth potential, the timer unit is arranged to break or make the connection between the pin of the live conductor and the corresponding connector to which the appliance is terminated. This gives maximum safety in operation and prevents relatively high voltages to be present in a connected appliance, other than when the appliance is to be energised. Most preferably, the time interval which is timed by the timer unit can be selected to be one of a number of pre-set time periods. For example, the timer may have built into it pre-set time periods of twenty, forty and sixty minutes and the user may select whichever of those periods is required, when energising the appliance to which the timer is connected. Conveniently, this is achieved by having the timer start control arranged as a button which is depressed once for the shortest pre-set period, a second time for the intermediate pre-set period and a third time for the longest pre-set period. For such an arrangement, depressing the button for a fourth time may turn off the timer, so interrupting the supply of electricity to the appliance. The push-button for starting the timed period may be located in a recess in the housing to reduce the likelihood of inadvertent or accidental depression of the button. Conversely, the button may be made relatively large and wholly apparent in order to show where pressure must be applied to start operating the timer, but provided with a spring loading to minimise the likelihood of inadvertent operation. Further, the housing may include one or more indicator lights, to show the operational status of the timer. For example, three LEDs may be provided, which are illuminated with successive presses on the button, to show what timed period has been selected. A further LED may give an indication that the timer has been plugged into an active mains outlet socket. Preferably, the housing includes an internal compartment to which access may be gained by removing a cover from that compartment. Provided within that compartment may be the connectors for terminating the appliance mains cable as well as a strain-relieving cable clamp for the appliance cable. Further, a fuse may be provided to protect the appliance, as with a conventional mains plug, which fuse is disposed within the compartment so that access may be gained thereto, on removing the cover. Access to the compartment advantageously is gained from the rear of the timer - that is to say, from the face of the timer from which the conducting pins project, for insertion into a mains outlet socket. In this way, access cannot be gained to the compartment when the timer is plugged into a mains outlet socket, even if the cover to the compartment has not been replaced. By way of example only, two specific embodiments of mains powered timer arranged in accordance with this invention will now be described in detail, reference being made to the accompanying drawings, in which:- Figure 1 is a diagrammatic isometric view of the embodiment of timer of this invention; Figure 2 is a rear face view of the timer of Figure 1, but with a compartment cover removed; Figure 3 diagrammatically illustrates the internal electrical arrangement of the timer; and Figure 4 illustrates a second embodiment of timer arranged on the same operating principles as that of Figures 1 to 3. The first embodiment of timer shown in Figures 1 to 3 comprises a moulded plastics material housing 10 of a generally rectangular configuration. One face 11 (designated the rear face) of the housing has electrical conductor pins 12,13,14 projecting at right angles therefrom, in a suitable arrangement to permit the housing to be plugged into a conventional UK domestic mains 13A flat pin outlet socket. Pin 12 connects to the live conductor of the socket, pin 13 to the neutral conductor and pin 14 to the earth conductor. On the rear face 11 of the housing 10, there is a removable cover 16, held in place by means of screws (not shown) which thread into holes 17 in the housing. Access to the compartment may be restricted by using security screws requiring the use of a corresponding tool if the screws are to be removed or replaced. Within the housing behind the cover 16 is a compartment 18, a terminal block 19 being disposed within that compartment. The terminal block 19 has three connector screws 20,21 ,22 for the conductors 23,24,25 of a mains cable 26. Within the housing, screw 21 is permanently connected to the neutral pin 13 and screw 22 to earth pin 14. Screw 20 may connect to the live pin 12 through a timer module 27 and a fuse 28. The fuse is in the form of a cartridge held in a carrier which may be prised from the housing compartment 18 if it is to be replaced or changed for another of a different value. A strain- relieving cable clamp 29 of a conventional design is provided in the compartment 18, to hold the end portion of the cable 26. The lower edge of the cover 16 is profiled to define in conjunction with the housing an aperture through which the cable 26 enters the compartment. The timer module 27 is located in the main body of the housing 10 and controls the operation of a relay (not shown) the contacts of which are in the circuit between the live pin 12 and screw 20 of the terminal block 19. The timer has three pre-set (during manufacture) timed intervals such as of twenty minutes, forty minutes and sixty minutes. The timer module includes a push-button 32 to initiate timing by the timer module. In this embodiment, the button is shown as projecting from front face 33, opposed to the rear face 11 of the housing. The outer end of the pushbutton may be located in a depression (not shown) in the housing, whereby the button may easily be depressed when a timed period is to commence, but the button is protected against accidental or inadvertent operation. Three LEDs 34,35,36 are provided above the push-button 32, respectively to indicate timed periods of twenty, forty and sixty minutes. LED 34 is illuminated on a first push on the button 32, to initiate the timing of the shortest period of twenty minutes; LED 35 is illuminated if the button 32 is pushed twice to initiate the timing of the intermediate period of forty minutes and LED 36 is illuminated if the button 32 is pushed three times to initiate the timing of the longest period of sixty minutes. If a period longer than the shortest is to be timed, the button must be pressed quickly in succession such that a longer period is deliberately selected. Though not shown, the timer may be provided with a further LED which is illuminated when the timer has been plugged into an active outlet socket, to show that the timer is ready to energise an appliance, just as soon as the pushbutton is depressed at least once. The timer module is electronic-based and in effect takes the form of a clock running at a pre-set frequency together with a counter for clock pulses. The counting of pulses commences when the push-button 32 is depressed, and this closes the relay (not shown) so completing the connection between the live pin 12 and the corresponding connector screw 20. Timing is concluded when a predetermined count has been reached, as selected by the appropriate number of button pushes at the start of the period the relay being released at this point so disconnecting connector screw 20 from live pin 12. As the timer module is electronic, it is possible that it might need to be reset, if for example the timer is left disconnected from the mains for a long period of time or should an over-voltage or over-load protection circuit within the module operate. For this purpose, a re-set pin 38 is provided, which may be pushed by a suitable tool in the direction of the arrow, from within the compartment 18. Figure 4 shows a second embodiment of timer of this invention, which is styled somewhat more like a conventional plug. This timer operates on the same principles as has been described above and so the operation of the timer will not be described in detail again here. The timer of Figure 4 has a housing 40 having a cable entry aperture 41 , the timer having a removable base plate (not shown) to give access to connection screws for terminating a mains cable 42 of the appliance to be energised. The conductor pins (not visible in Figure 4) project through the removable base plate so that the timer may be plugged into a mains outlet socket in a conventional way, much like a standard plug. The outer face 43 of the housing 40 has a semi-circular push-button 44, over which are provided three sector-shaped LEDs 45,46,47, respectively to indicate timed periods of twenty, forty and sixty minutes. A suitable index mark is carried on the housing next to each LED. In order to show that the timer is plugged into an active mains outlet socket, a further LED (not shown) is disposed beneath the push-button 44, which thus will be illuminated when the timer is ready to start timing a pre-set period. As with the first embodiment of timer, this embodiment is intended for essentially permanent connection to the mains cable of an appliance such as an electric iron, a hair styling device or the like. However, the timer may be removed from that mains cable and fitted to the mains cable of some other appliance, if for example the first appliance ceases working or is being updated. Both embodiments of timer significantly enhance safety of an electrical appliance which includes a heating element. No longer is it possible for electricity to be supplied indefinitely to the appliance, since there is no bypass for the timed period. Once fitted to the mains cable, the appliance may be operated only for the maximum permitted period of the timer - though if a user wishes to have the appliance operate for longer, it would of course be possible to initiate another timed period. Though the timers described above have all been pre-set with timed intervals of twenty, forty and sixty minutes, other periods may be pre-set during manufacture, if required. Further, it would be possible for the timer to include a pre-selecting control accessible for example within the compartment, to choose two or more different sequences of timed periods. For instance, the timer could be adjusted to time periods of twenty, forty and sixty minutes or of ten, twenty and thirty minutes.

Claims

1. A mains-powered timer comprising a housing provided with conducting pins arranged to permit the timer to be plugged into a standard mains outlet, connectors internally of the housing for terminating a mains cable passing into the housing, an electronic timer unit provided within the housing and arranged to time a pre-set time interval, the timer unit connecting at least one conducting pin of the housing to a corresponding connector during timing of the pre-set interval, and a manually operable timer start control accessible from outside the housing and arranged to start the timing of said pre-set interval.

2. A timer as claimed in claim 1 , wherein the timer unit is arranged to make and break a connection between one pin of the housing and a corresponding connector to which a mains cable is terminated.

3. A timer as claimed in claim 1 or claim 2, wherein the time interval which is timed by the timer unit is selectable to be one of a number of pre-set periods.

4. A timer as claimed in claim 3, wherein the required time interval is selected by operation of the timer start control, on initiating a timed period.

5. A timer as claimed in claim 4, wherein the manual control comprises a push-button accessible from externally of the housing and the pre-selection of a required time period is performed by depressing the button an appropriate number of times.

6. A timer as claimed in claim 5, wherein the push-button is located within a depression within the housing.

7. A timer as claimed in any of claims 4 to 6, wherein individual indicators are provided to show the selected time period.

8. A timer as claimed in claim 7, wherein each indicator comprises an LED which is illuminated to show the selected time period.

9. A timer as claimed in any of the preceding claims, wherein the housing includes an internal compartment and a removable cover for that compartment, the connectors for terminating a mains cable being provided within that compartment.

10. A timer as claimed in claim 9, wherein one or more security screws are provided to secure the cover in position closing the compartment.

11. A timer as claimed in any of the preceding claims, wherein an indicator is provided to show when the timer is plugged into an active mains outlet socket.

12. A timer as claimed in claim 1 and substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.