WO2000002218A1

WO2000002218A1 - A timer unit

Info

Publication number: WO2000002218A1
Application number: PCT/GB1999/002144
Authority: WO
Inventors: Ronald Weston Gretton
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-07-06
Filing date: 1999-07-05
Publication date: 2000-01-13
Anticipated expiration: 2001-01-06
Also published as: GB2340625A; GB9814551D0

Abstract

A timer unit includes: input pin connectors for electrically connecting the unit to a domestic power socket; an electrical outlet for connecting an appliance thereto; switch means for electrically connecting the input pins to the outlet of said unit; and count-down timer means operable to count down for a predetermined time period and after the predetermined time period to operate the switch means to electrically isolate said input pin connectors from said outlet. A reset mechanism prevents inadvertent electrical reconnection of an appliance in the event of a power loss and restoration to the timer unit.

Description

A TIMER UNIT

The present invention relates to timer units and in particular to timer units for controlling the operation of mains-powered appliances.

In the domestic environment it is often desirable to control electrical appliances by time switches. For example, it is well known to install time switches to switch lights on and off at predetermined times of the day or night, thus indicating occupancy of an empty property.

Known time switches generally operate in similar ways. A timer mechanism is often incorporated within a housing which can be plugged directly into a wall socket and into which the appliance can then be plugged in a "piggy-back" type arrangement. The time switch is programmed by the user to switch an appliance on at a required time and to switch the appliance off at a later time. The programming of the time switch is often a fiddly operation which is prone to errors and is difficult, if not impossible, for partially sighted or handicapped persons.

Many appliances used in the domestic environment could constitute a hazard when inadvertently left switched on, or even when simply left connected to the mains power supply, for extended periods of time. More generally, appliances left connected to the mains supply for extended periods of time when not in use results in wastage of electricity and unnecessary potential hazard.

Examples of appliances which could cause a fire hazard if left switched on unattended are irons, hair curling tongs, heated rollers, fan or radiant heaters, electric blankets, kettles etc. Examples of appliances which might constitute a safety hazard if left connected to the main power supply when not in use are electric carving knives, power tools and the like. This is particularly so where small children, disabled or handicapped persons are present.

Thus, it would be desirable to provide a time switch which automatically disconnects an electrical appliance from the mains power supply after a predetermined period. Although such a function could be provided by a conventional programmable time switch as discussed previously, it will be understood that such an arrangement is inconvenient as the unit would have to be set or programmed each time of use. As discussed above, such programming is also difficult for many persons.

It is an object of the present invention to provide a time switch for use with a domestic electricity supply which will automatically disconnect an appliance a predetermined period of time after first connection of the appliance to the mains supply.

It is a further object of the invention to provide such a time switch that is extremely simple to use by both able-bodied persons and disabled persons, including blind persons and those with a physical or mental handicap.

It is a further object of the invention to provide a very low cost time switch which can be readily be provided as an adaptor to existing plug and socket arrangements, or as a replacement appliance plug. It is a further object of the invention to provide a time switch that prevents inadvertent or unintentional reconnection of the appliance to the main power supply.

According to one aspect of the present invention there is provided a timer unit comprising: input pin connectors for electrically connecting the timer unit to a domestic power socket; an electrical outlet; switch means for electrically connecting said input pin connectors to the outlet; count-down timer means being operable to count down for a predetermined time period and after said predetermined time period to operate said switch means to electrically isolate said input pin connectors from said outlet.

According to another aspect of the present invention there is provided a timer unit comprising: connection means for electrically connecting the timer unit to a domestic power socket; an electrical outlet; switch means for electrically connecting said electrical outlet to said connection means; count-down timer means being operable to count-down for a predetermined time period and after said predetermined time period to operate said switch means to electrically isolate the timer unit electrical outlet from said domestic power socket. In a preferred embodiment, the count-down timer means is activated after the timer unit is connected to the domestic power socket,

> either through insertion of the plug into the socket, through switching the domestic power socket on, or by depressing a power reset button on the timer unit, or a combination thereof.

In another embodiment, the timer unit requires no setting by the user. The predetermined count-down time period is non-adjustable by the user and, for ease of use by handicapped persons, is preferably clearly mdicated by the shape, configuration or colour of the unit housing, or by pattern thereon.

In a preferred embodiment, the timer is incorporated within a plug adapted to be fitted directly to the mains cable of the appliance.

In another embodiment, the timer unit is provided as a single housing incorporating the input pin connectors for connection to a domestic power outlet and a socket for receiving an appliance plug.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which:

Figure 1 shows a perspective view of a timer unit, separate wall socket and separate appliance plug according to one arrangement of the present invention; Figure 2 shows a perspective view of a timer unit, separate wall socket and separate appliance plug according to another arrangement of the present invention;

Figures 3a, 3b and 3c respectively show front, side and rear views of a timer unit incorporated within an appliance plug; Figure 4 shows a timer unit, arranged in an in-line configuration; and

>

Figure 5 is a wiring diagram of the electrical circuit of the timer unit of figure 1.

With reference to figure 1, a timer unit 1 comprises a housing 2 incorporating, on one face, a plurality of input pin connectors 3, 4 arranged in a standard UK 13 amp domestic plug configuration. On the opposing face is provided an electrical outlet arranged in a corresponding standard UK 13 amp socket configuration, including pin receivers 6, 7 and 8. A timer mechanism is provided within the housing, which will be described in detail hereinafter.

The housing includes, on a conveniently accessible outer face 10, a reset switch 11 and warning light 12, the operation of which will be described hereinafter.

The input pin connectors 3, 4 (and a third pin, not visible in the drawing) are adapted to be received into a standard wall socket 15. The electrical outlet 6, 7, 8 is adapted to receive an appliance plug 16.

With reference to figure 2, a similar timer unit 21 is shown, which further includes, embossed on a face 22 thereof, a relief moulding 23 indicating a timer count-down period. This can be read visually and also by touch, in the case of visually handicapped persons.

With reference to figure 3, a similar timer unit 31 is shown. In this arrangement, the timer unit 31 is configured as a single plug unit suitable for direct connection to an appliance cable 32. The input pin connectors 33, 34 and 35 are arranged in a standard UK 13-amp domestic plug configuration. The front face 36 of the plug 31 includes a reset button 37 and a warning light 38, the functions of which will be described hereinafter.

With reference to figure 4 there is shown a timer unit 41 comprising a housing 42 in line with an appliance cable 43, terminated in a standard domestic plug 44. This embodiment may also include a reset switch 11 and warning light 12 as shown.

Although the embodiments described in connection with figures 1 to 4 are all shown conforming to UK standard domestic power plug and socket configurations, it will be understood that other arrangements in use around the world could equally be used.

The timer unit of each of the embodiments described above is provided with a count-down timer which is preset to a predetermmed time period, which time period is preferably clearly displayed on the timer unit housing 21, 31 or 41. Preferably, the predetermined time period is displayed as a relief moulding so that it can be read by partially or non- sighted persons. The relief moulding could form the overall outer shaping of the timer housing. The relief moulding could also comprise Braille. The timer unit housing could be colour coded according to the desired time period in addition to or instead of the relief moulding.

The timer unit of each of the embodiments described above is also provided with an internal switch which is acmated to electrically connect the input pins 3, 4, 5 to the electrical outlet 6, 7, 8 when the timer unit 1, 21, 31, 41 is first connected to a power outlet. The internal switch is also controlled by the count-down timer unit to electrically disconnect the input pins 3, 4, 5 to the electrical outlet 6, 7, 8 upon expiry of the pre-

> programmed count-down time period.

The actuation of the internal switch to electrically connect the input pins to the electrical outlet and commencement of the count-down timer operation may be effected automatically as soon as the timer unit 1 is plugged in and power applied to the input pins.

However, in a preferred embodiment, actuation of the switch and commencement of the count-down timer operation is effected by operation of a manual reset button 11 such as that shown in figures 1 to 3.

This is an important safety feature which prevents inadvertent connection or re-connection of an appliance. For example, a timer unit might be plugged into a wall socket 15 with an appliance connected.

Upon expiry of the count-down time period, the appliance would be automatically electrically disconnected from the power supply. Without a manual reset function, in the event of a mains power failure and on resumption of the domestic power supply, a timer unit could be caused to detect a power up condition and electrically reconnect the appliance.

Under some circumstances, this could be dangerous and negate some safety benefits of the timer unit.

However, where provision of the manual reset button 11 is not desired, another embodiment of the invention provides for the reset function to be provided by a microswitch 50. Microswitch 50 is incorporated into the timer unit housing in such a way that the action of plugging the unit into a socket toggles the microswitch. This triggers actuation of the internal switch and commencement of the count-down timer operation. In this case, any disruption of the domestic power supply while the timer unit is plugged into a socket will still cause the appliance to remain electrically disconnected even when the domestic power supply is restored. This is because the count-down timer and internal switch will not be re-enabled until the microswitch 50 has again been toggled. Thus, to reconnect the appliance and restart the count-down timer requires the timer unit to be unplugged and re-plugged in.

The microswitch 50 could be provided on the rear face 51 of the timer unit (as shown in figure 3) or alternatively could be provided within the housing behind a spring loaded input pin connector 33, 34, 35. In the embodiment of figure 1 , the microswitch 50 could be provided inside the pin receiving holes 6, 7, 8.

The warning light 12 can be used to confirm operation of the countdown timer and that the electrical outlet of the timer unit is live.

With reference now to figure 5, a circuit 100 suitable for implementing one embodiment of the invention is shown. The timer unit circuit 100 is connected to the mains supply though a fuse 124 and a filter comprising inductors LI, L2, L3, L4 and capacitors Cl, C2. The filter 126 reduces the effect of incoming and outgoing electromagnetic interference.

A programmable integrated circuit microcontroller 130 is the main controlling element of the circuit 100. The software programmed into microcontroller 130 performs a number of functions. When the power is applied to the circuit, microcontroller 130 samples the incoming AC waveform. At the zero crossing point of the waveform, the microcontroller switches on a triac switch 132 to apply power the load 110, which of course represents the appliance plugged in.

A count-down timer internal to the microcontroller is started. When a pre-determined time period has elapsed, the microcontroller again samples the incoming AC waveform. At a zero crossing point of the waveform, the triac switch 132 is switched off and the microcontroller 130 enters a sleep mode.

Switching the triac 32 when the AC waveform is near zero voltage is advantageous because it reduces load switching transients. The countdown timer in microcontroller 130 is derived from an internal 4 MHz oscillator. Spare input or output connections of the microcontroller may be used to program predetermined count-down time mtervals by connection to a reference voltage V_ss. This would enable the same circuit to be used in the manufacture of timer units having different count-down time periods.

The microcontroller 30 requires a nominal input voltage V_DD of 5V in order to operate. This voltage is derived directly from the mains by a series resistor dropping chain 136 comprising resistors Rl, R2 and R3. The use of three resistors spreads the energy dissipation. The AC supply is then half- wave rectified by a diode Dl and smoothed by capacitor C4. A zener diode 142 regulates the DC supply to the microcontroller to a nominal 5V.

Capacitor C3 is mounted as close to the input current supply pins as possible so that it is effective in the case of high energy transients. The zener diode 142 and rectifier diode Dl also advantageously have a protecting effect with the three series resistors Rl , R2 and R3 absorbing

> most of the transient energy due to their inherent high value.

The zero-crossing point sampling circuit 140 provides a unidirectional sample of the incoming AC waveform at a suitable level as specified by the input/output voltage limits for the microcontroller, for low level triac switching.

The triac 132 is switched on when the IC pin for driving the triac gate falls to zero with respect to reference voltage V_ss. The triac gate is thus fed from a nominal 5V source between the gate and the cathode. When the IC pin is switched towards the supply voltage V_DD, there will be approximately zero volts between the gate and the cathode of the triac and the triac will switch off.

In the preferred embodiment, the count-down timer is a solid state timer, although any other suitable timer may be employed.

It will be understood that the switching capacity of the timer unit may be any suitable capacity (voltage and current) for the domestic power supply and appliances with which it is to work. If desired, the load switching might be provided via a relay rather than direct triac switching.

It will be understood that the switch means may be a multi-pole configuration operative to fully electrically isolate two or more of the input pins from the electrical outlet or, as shown in connection with figure 5, to electrically isolate only a live pin from the electrical outlet in a single pole configuration. In one embodiment of the invention it is envisaged that the plug body 31 or timer unit housing 1 or part thereof may be formed in the shape of numbers which indicate the length of time the appliance 18 will be in operation before resetting of the timer is required. This is particularly advantageous for the partially sighted user.

The different models of timer could also be colour coded, different colours each representing the length of time for which the timer will be activated.

As discussed above, the timer unit is preferably not provided with external timer controls. It is controlled only by access to a power supply or removing the power supplied to the unit. However, in another embodiment, the timer unit 1, 21, 31, 41 could be provided with a rotating encoder switch or knob allowing easy setting of the timer to one of a number of discrete count-down time periods. This would allow the timer to be easily programmed in prefixed increments as required. For example the increments could be 15, 30, 45, 60, 90, 120 and 150 minutes.

In another arrangement, the encoder switch might be replaced by miniature DIP switches or similar which can be factory set or set when the timer plug is fitted to an appliance.

In a further embodiment of the invention, the timer circuit 100 could be replaced with a low voltage control circuit.

In a further embodiment, the timer unit may incorporate a buzzer or other audible warning device. The audible warning device would be programmed to sound just prior to the completion of the count-down timer period, in order to notify the user when the appliance is about to be disconnected. In the case of the timer unit having a reset button 11, the

> timer count-down might then be reset by the user without interruption of the supply to the appliance.

Claims

CLAIMS>

1. A timer unit comprising: input pin connectors for electrically connecting the timer unit to a domestic power socket; an electrical outlet; switch means for electrically connecting said input pin connectors to the outlet; count-down timer means being operable to count down for a predetermmed time period and after said predetermined time period to operate said switch means to electrically isolate said input pin connectors from said outlet.

2. A timer unit according to claim 1 further including reset means operable to initiate commencement of the count-down timer means and to operate said switch means to electrically connect said input pin connectors to the outlet after said input pin connectors have been connected to a said power socket.

3. A timer unit according to claim 2 wherein the reset means comprises a push switch on an outer face of the timer unit housing.

4. A timer unit according to claim 2 wherein the reset means comprises a microswitch which is mechamcally toggled by the action of plugging in the timer unit into a said power socket.

5. A timer unit according to claim 4 wherein the reset means is provided internally of the timer unit housing.

6. A timer unit according to any preceding claim wherein said countdown timer means is deactivated after the predetermined time period has

> lapsed.

7. A timer unit according to any preceding claim adapted to co-operate with a standard domestic socket.

8. A timer unit according to any preceding claim wherein the electrical outlet is adapted for connection to a domestic appliance.

9. A timer unit according to any preceding claim wherem at least a part of the timer unit housing is formed in a shape providing a visual and tactile indication of the duration of the count-down time period.

10. A timer unit according to claim 9 wherein an external face of the timer unit includes a relief moulding indicating the duration of the countdown time period

11. A timer unit according to any preceding claim wherein the duration of the count-down time period is not alterable externally of the timer unit.

12. A timer unit according to any preceding claim wherein the timer unit is housed within a domestic appliance plug so as to permit direct connection to an appliance flex.

13. A timer unit comprising: connection means for electrically connecting the timer unit to a domestic power socket; an electrical outlet; switch means for electrically connecting said electrical outlet to said connection means; count-down timer means being operable to count-down for a predetermined time period and after said predetermined time period to operate said switch means to electrically isolate the timer unit electrical outlet from said domestic power socket.

14. A timer unit substantially as described herein with reference to the accompanying drawings.