GB2155210A - Power supply circuit for an atmospheric vaporiser - Google Patents

Abstract

An atmospheric vaporiser 1 having an electrical heater 25 for heating a reagent-containing container and means for controlling the supply of electric current to the heater 25 comprising a time switch 33 having "on" and "off" states and a thermostat 32 for controlling the supply of electric current to the heater 25 in dependence on the temperature sensed in the vicinity of the reagent-containing container is provided with an override switch 110 for enabling electric current to be supplied to the heater 25 when the interval time 33 is in its "off" state and the temperature responsive means is in a condition to allow supply of electrical current to the heater 25. The push button 110 energises self holding relay 102 which maintains the heater energised until the thermostat opens. <IMAGE>

Description

SPECIFICATION An atmospheric vaporiser This invention relates to an atmospheric vaporiser of the kind comprising electrical heating means for heating a reagent-containing container and control means for controlling the supply of electrical current to the electrical heating means including an interval time switch having an on state, for enabling heating of the container during at least one, typically but not essentially presettable, time interval, and an off state, and temperature responsive means allowing or preventing supply of electrical current to the heating means in dependence on the temperature sensed in use of the vaporiser in the vicinity of the reagent-containing container.In this specification, the term "atmospheric vaporiser" means a device which serves to vaporise one or more reagents, such as humidifiers, deodorisers, perfumes, therapeutic preparations, insecticides and fly repellents, into the atmosphere, for example for humidifying the atmosphere, for improving the fragrance of a room, to provide relief to persons suffering from respiratory troubles, and/or to eliminate insects and other pests.

A known atmospheric vaporiser of the kind referred to is disclosed in U.K. published patent application No. 2080111A. However this known vaporiser suffers from the disadvantage that is only operational to heat the reagent during pre-set time intervals set on the interval time switch and it is not possible to override this time switch.

According to the present invention an atmospheric vaporiser of the kind referred to is characterised in that the control means further includes override switch means effective on acutation thereof to enable electrical current to be supplied to the heating means during a period when the interval time switch is in its off state and the temperature responsive means is in a condition to allow supply of electrical current to the heating means, supply of current to the heating means occasioned by actuation of the override switch means being terminated, when the time switch is in its off state, by the temperature responsive means changing from a condition allowing, to a condition preventing supply of electrical current to the heating means, any subsequent supply of electric current to the heating means after such a termination only being occasioned by a further actuation of the override switch means or by the interval time switch changing into its on state.

The present invention makes use of the fact that a heating control system incorporating a temperature responsive means, e.g. an automatic temperature-control switch, uses on-off heating control. It has been found that in an atmospheric vaporiser using an automatic temperature-control switch for on-off heating control, a useful degree of heating is obtained if the heating means is activated only once, for a relatively short period of time, until the temperature sensed by the temperature-control switch exceeds a first temperature, e.g. 150 C. The heating means is not automatically re-activated when the temperature-control switch reverts back to a condition allowing supply of electrical current to the heating means as the temperature sensed by the temperature-control switch drops below a second temperature, e.g. 135cm, unless, during the period that the temperature-control switch is in a condition to prevent supply of electrical current to the heatng means, the interval time switch enters into the, or one of the time intervals(s) - i.e. it changes from its off state to its on state.

It is possible for the heating means to directly heat the reagent-containing container. However, it is preferred that the atmospherc vaporiser includes an open-topped receiver heated by the heating means, the reagent-containing container being received, e.g. in a loose-fit, in the receiver and being removable therefrom. Preferably the open-topped receiver and the reagent-containing container are metallic.

Suitably the temperature responsive means comprises a temperature sensing device (e.g. a thermostat) in the vicinity of (e.g. mounted oni, the reagent-containing container, and a relay, controlled by the temperature sensing device, having a first circuit means and switching means controlled by the first circuit means. Conveniently the first circuit means is connected in parallel with the electrical heating means, this parallel combination being connected in series with the temperature sensing device and a parallel combination of the interval time switch and the override switch means. Connection means are provided for coupling an a.c.

supply, e.g. a mains supply, into the series circuit, the switching means of the relay being connected between a connection means of the a.c. supply and a point between the temperature sensing device and the parallel connection of the interval time switch and the override switch means.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawing, the sole figure of which shows a circuit diagram of a control circuit for controlling the heating of heating of an atmostpheric vaporiser according to the invention.

in one embodiment of the invention, the atmospheric vaporiser shown in Figures 1 and 2 of the aforementioned U.K. published patent application No. 208011 1A is modified by the modification of the control circuit for controlling the operation of the electrical heating element 25. (In this specification all reference numerals below 100 and all capital reference letters refer to items shown in Figures 1 to 4 of the aforementioned U.K. published patent application No. 2080111A. Reference numerals over 100 refer specifically to items shown in the sole figure accompanying the present application.) In particular, with reference to the sole figure accompanying the present application, there is shown a control circuit, generally designated 101, for incorporation in an atmospheric vaporiser according to the invention.The circuit 101 includes temperature responsive means in the form of a thermostatic device comprising a temperature sensor 32 (e.g. a temperature-control switch) having terminals 109 and 111 and an armature relay gen erally designated 102. The relay 102 has a coil 103 wound on a soft-iron core (not shown), a fixed contact 105, and a pivoted armature (not shown) carrying a movable contact 104 movable into and out of contact with the fixed contact 105 depending on whether or not the coil 103 is energised. In the unenergised state of the coil 103, the contacts 104 and 105 are spaced apart so as not to be in electrical contact with each other.

The fixed contact 105 is conected to a live terminal 106 of an a.c. mains supply 107 having a neutral terminal 108. The movable contact 104 is connected to the terminal 109 of the temperature sensor 32.

The terminal 109 is connected to the terminal 106 via a parallel combination of a an electro-mechanical timer switch, generally designated 33, having a movable switch contact 133 and a normally open push-button override switch, generally designated 110, and a fuse 120. The other terminal 111 of the sensor 32 is connectaed to the terminal 108 via the heating element 25. A coil 103 is arranged in parallel with the element 25 and a neon indicator lamp 112 is arranged across the element 25 to signify when current flows through the element 25.

The temperature sensor 32 which is in the form of a temperature-control switch is typically arranged to remain in a closed state, during a heating cycle, until a first temperature, e.g. 150 C, is sensed. When the first temperature is attained, the temperature sensitive switch opens and remains open until the sensed temperature drops to a second temperature, e.g. 135 C, whereupon the switch closes again.

In use of an atmospheric vaporiser according to the invention, the interval timer switch 33 is typically preset to turn on twice during each 24-hour cycle. For example in the case where the vaporiser vaporises insecticides into the atmosphere ther timer switch 33 may be set to come on (i.e. the contact 133 is closed) for one period during the night, e.g. from midnight to 6.00 a.m., when insects are generally most active, and for a shorter period during the morning, e.g. from 11.00 a.m. to midday, after vacuum cleaning. At all other times the timer switch will remain off (i.e. the contact 133 is open - as shown). Assuming that the push-button switch 110 is not actuated, the heating element 25 is only supplied with electrical current when the time switch 33 is on (i.e. contact 133 is closed) and the sensor 32 (i.e. the temperature-control switch) is also closed.In effect the temperature-control switch is repeatedly automatically opened and closed during each time interval that the time switch 33 is on so that, by automatic on-off control, the reagent in the container 42 is always maintained at a temperature above its vaporising temperature.

If, during a period of time that the timer switch 33 is off (i.e. the contact 133 is open), the pushbutton switch 110 is manually depressed, a current flow path is provided, for the time that the pushbutton switch 110 remains depressed, around a first circuit comprising the a.c. mains supply 107, the parallel combination of the coil 103 and the heating element 25, the sensor 32 and the switch 110. The flow of electrical current through the coil 103, caused the armature of the relay 102 to pivot so that the contacts 104 and 105 make contact with each other. Once this occurs a current flow path is established around a second circuit comprising the a.c. mains supply 107, the parallel combination of the coil 103 and the heating element 25, the temperature sensor 32 and the making contacts 104 and 105.Once current flows in this second circuit, opening of the switch 110, by releasing the pressure on the depressed button, does not prevent supply of electrical current to the element 25 since th flow of current in the second circuit is not interrupted. The supply of current to the element 25 is, however, terminated when the first temperature is sensed by the sensor 32 so that the temperaturecontrol switch opens causing the contacts 104 and 105 to break. As the temperature sensed by the sensor 32 falls to the second temperature, the temperature-control switch closes. However, provided that the timer switch 33 is still off (i.e. the contact 133 is open) and that the push-button switch 110 is not depressed, current will not now flow thorugh the element 25 since the switches 104 and 105 are now in a break condition.It will be appreciated that the switches 104 and 105 can only re-establish contact with each other when either of the switches 33 and 110 is closed.

By appropriate choice of the first and second temperatures for controlling the sensor 32, and provided that the thermal capacity of the receiver 22 is sufficient, the reagent is able to remain in a state where it is vaporised for a number of minutes.

By way of example if a lindane crystal (99.5% pure) is used as the reagent, it normally takes approximately 7 minutes to heat the crystal to a first temperature of 150 C. Under automatic thermostatic control during each on period of the time switch 33, the lindane crystal is automatically reheated when the temperature of the crystal drops to the second temperature of 135 C. if, however, the override switch 110 is manually actuated when the time switch 33 is off, the lindane crystal is heated up to the first temperature of 1500C in approximately 7 minutes as before. However by the time that the crystal has cooled sufficiently so as not to be vaporised after the current supply to the heating element 25 has ceased, a period of approximately 15 minutes has elapsed when the crystal has been in an active condition. This is considered to be sufficient time to kill a swarm of insects which arrive in a room between the normal on periods of the time switch 33.

The time switch 33 as shown in the figure accompanying this specification is a conventional electro-mechanical timer switch having one or more pre-settable "on" time intervals (i.e. the duration of the or each "on" time interval can be adjustably pre-set). The contact 133 is arranged to be closed by the a.c. mains powered motor m of the time switch 33. In other embodiments of the invention, the timer switch could be replaced by an elec tronic timer, e.g. typically incorporating integrated circuit means mounted on a printed circuit board, either designed to continually switch between "on" and "off" states of predetermined intervals (e.g. 1 hour "on" followed by 3 hours "off" then 1 hour "on" and so on) or having "on" and "off" intervals of presettable durations.Furthermore other forms of relay 102, e.g. a solid-state relay, such as a triac, can be used as part of the temperature responsive means. For example a triac could be used to control the electric current supplied to the load in dependence on the voltage supplied to the gate electrode of the triac. In particular this gate voltage would be controlled by a thermostat sensing the temperature in the vicinity of the reagent-containing container.

Apart from the improved control of the heating element 25, an atmospheric vaporiser according to the invention is similar to the vaporiser described in Figures 1 and 2 and in Figures 3 and 4, when provided with an interval time switch, of the previously mentioned U.K. published patent application No. 2080111A. All embodiments and modifications of the vaporiser disclosed in this published patent application and which fall within the scope of the present invention are incorporated herein by way of reference.

Claims (15)

1. An atmospheric vaporiser comprising electrical heating means for heating a reagent-containing container and control means for controlling the supply of electrical current to the electrical heating means including an interval time switch having an on state, for enabling heating of the container during at least one time interval, and an off state, and temperature responsive means allowing or preventing supply of electrical current to the heating means in dependence on the temperature sensed in use of the vaporiser in the vicinity of the reagent-containing container, characterised in that the control means further includes override switch means effective on actuation thereof to enable electrical current to be supplied to the heating means during a period when the interval time switch is in its off state and the temperature responsive means is in a condition to allow supply of electrical current to the heating means, supply of current to the heating means occasioned by actuation of the override switch means being terminated, when the time switch is in its off state, by the temperature responsive means changing from a condition allowing, to a condition preventing supply of electrical current to the heating means, any subsequent supply of electric current to the heating means after such a termination only being occasioned by a further actuation of the override switch means or by the interval time switch changing into its on state.

2. An atmospheric vaporiser according to claim 1, in which the or each time interval is pre-settable.

3. An atmospheric vaporiser according to claim 1 or 2, in which said temperataure responsive means comprises an automatic temperature-control switch using on-off heating control.

4. An atmospheric vaporiser according to any of claims 1 to 3, including an open-topped receiver for removably receiving the reagent-containing container.

5. An atmospheric vaporiser according to claim 4, in which the open-topped receiver is arranged to be heated by the heating means for heating the reagent-containing container.

6. An atmospheric vaporiser according to claim 4 or 5, in which the open-topped receiver and the reagent- containing container are metallic.

7. An atmospheric vaporiser according to any of the preceding claims, in which the temperature responsive means comprises a temperature sensing device in the vicinity of the reagent-containing container, and a relay, controlled by the temperature sensing device, having a first circuit means and switching means controlled by the first circuit means.

8. An atmospheric vaporiser according to claim 7, in which the first circuit means is connected in parallel with the electrical heating means, this parallel combination being connected in series with the temperature-sensing device and a parallel combination of the interval time switch and the override switch means.

9. An atmospheric vaporiser according to claim 8, in which connection means are provided for coupling an a.c. supply into the series circuit, the switching means of the relay being connected between a connection means of the a.c. supply and a point between the temperature sensing device and the parallel connection of the interval time switch and the override switch means.

10. An atmospheric vaporiser according to any of the preceding claims, in whih the interval time switch comprises an electro-mechanical time switch having at least one pre-settable time interval.

11. An atmospheric vaporiser according to any of claims 1 to 9, in which the interval time switch comprises an electronic timer.

12. An atmospheric vaporiser according to claim 11, in which the electronic timer has at least one presettable time interval.

13. An atmospheric vaporiser according to claim 1 or claim 12 when directly dependent upon claim 1, in which the temperature responsive means comprises a temperature sensing device and a solid state relay device controlled by the temperature sensing device.

14. An atmospheric vaporiser according to claim 13, in which the solid state relay device comprises a triac.

15. An atmospheric vaporiser constructed and arranged substantially as herein described with reference to the accompanying drawing.